Toxicology (Part 3)

1. Introduction

This chapter sets out the guidelines for submitting toxicology data—or scientific argument in the absence of data—as part of applications for approval of new active constituents, registration of veterinary chemical products, variation of registered veterinary chemical products, or application for permits to use veterinary chemical products.

Toxicology data and/or scientific argument provide information on the potential human health hazards arising from proposed uses of veterinary chemical products. This information is important in establishing relevant health recommendations for safe use of veterinary chemical products, including:

• acceptable daily intakes
• acute reference doses
• poison scheduling
• first aid instructions
• safety directions
• warning statements
• re-handling statements
• other limitations on use (for example, restraints, restrictions).

2. Reference materials

We have provided details of documents referred to in this chapter (including codes and standards) in the 'References' section, including bibliographic details and, where appropriate, ISBN and purchase information. You should be aware that many of these documents are updated regularly and for this reason we have not supplied dates in the text. Therefore, it is important to ensure that you use the latest edition of reference materials.

3. VICH guidelines

We have adopted the following relevant guidelines published by the International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Products (VICH). These VICH guidelines, which refer to Organisation for Economic Co-operation and Development (OECD) Guidelines for the Testing of Chemicals (see 'Conduct of studies'), may be useful when you are generating data in support of your application.

The VICH studies to evaluate the safety of residues of veterinary drugs in human food are:

• Reproduction testing: VICH Guideline no. 22
• Genotoxicity testing: VICH Guideline no. 23
• Carcinogenicity testing: VICH Guideline no. 28
• Repeat-dose toxicity (90 days) testing: VICH Guideline no. 31
• Developmental toxicity testing: VICH Guideline no. 32
• General approach to testing: VICH Guideline no. 33
• Microbiological ADI: VICH Guideline no. 36

4. Types of applications

The toxicology data elements that you should address in your application depend on the nature of the application. The nature of the application determines which Part 3 (toxicology) data module is appropriate.

Each module has a number of toxicology data elements, which are described in detail in the legislative instrument. A comprehensive assessment comprises a full toxicology data package, containing all of the data elements listed under the heading ‘Data elements for a comprehensive Part 3 (toxicology) submission’. A reduced assessment or limited assessment comprises a subset of the data elements contained in a comprehensive assessment.

5. Data elements and guidelines

The data you generate and submit for evaluation is assessed to identify the immediate hazards to the user, and to enable the classification for poison scheduling or to ensure that the poisons scheduling remains appropriate, and to set directions for the safe use of the product.

5.1. General recommendations

5.1.1. Submission

You should submit toxicology data packages according to the procedures outlined in the regulatory guidelines. Submissions that deviate significantly from the procedures outlined in the regulatory guidelines may be of reduced or no regulatory value.

The data elements for a comprehensive part 3 toxicology submission are shown below. All data elements should be addressed with the submission of data or scientific argument.

The documentation you submit to us should be complete and well organised. It should be presented in sufficient detail to allow independent scientific assessment (for example, you should provide individual animal data when available). You should supply copies of original reports. Summaries, abstracts and published material alone usually do not contain adequate detail for independent scientific evaluation. Data that do not enable independent evaluation may be of reduced or limited regulatory value, or may be determined to be inappropriate for regulatory purposes.

In certain cases, you may provide scientific argument based on accepted scientific principles or data published in peer-reviewed journals in lieu of submission of toxicology studies.

If you do not believe that a particular data element is necessary, you may request a data waiver. In such cases, you should maintain the data headings and provide a valid scientific argument as to why the data element should not be included. The regulatory value of scientific arguments for waiver requests will be assessed on their merits.

For some applications, certain studies may not be relevant because of the type of active constituent or product being proposed for registration, or because of the specific veterinary situation where the product is intended for use. For example, carcinogenicity testing may not be relevant for an active constituent that is not intended for food-producing use (see ‘Data elements’ for further information).

You should not omit any report that could influence the toxicology assessment of the substance.

5.1.2. Applications and/or assessment involving other regulatory authorities

You should include details of any applications for the same active constituent or product lodged with other regulatory agencies, either in Australia or overseas. Where available, you should provide the same data relied on by the other regulatory agency (noting the general recommendations and guidance outlined in previous sections of this guideline) in determining the results of these applications and coming to subsequent regulatory decisions. Where available, you should also provide any other reports or documentation related to the chemical or product. If use of the chemical or product has been considered unfavourably by an overseas regulatory body, you should provide all details and submit a scientific argument discussing this information in the context of the Australian approval of the active constituent or registration of the veterinary chemical product.

The regulatory agencies across the different chemical sectors in Australia and overseas often operate under differing risk paradigms, and data generated for the purpose of one regulator may not be applicable within other regulatory sectors. You may also provide data generated for non-veterinary products such as human medicines. Data generated will be evaluated on their merits and may be of reduced or no regulatory value, as data guidelines differ between prescription and over-the-counter human medicines.

5.1.3. Conduct of studies

All toxicity studies should be conducted in accordance with the adopted Organisation for Economic Co-operation and Development (OECD) Guidelines for the Testing of Chemicals or other recognised test guidelines—for example the US Environmental Protection Agency’s Office of Chemical Safety and Pollution Prevention health effects test guidelines, the European Union’s guidelines or the Japanese Ministry of Fisheries and Food guidelines—and in accordance with an acceptable code of good laboratory practice (OECD or equivalent). You should provide certification to this effect. Studies that are not compliant with good laboratory practice or recognised guidelines will be considered case by case on their scientific merit, and may be of reduced or no regulatory value.

Each study should clearly identify the name and address of the laboratory that performed the study, the names of the responsible scientists, the report number, the dates when the study was performed and the date the report was written.

Studies should use testing regimes that cover the most likely routes of human exposure.

Where appropriate, studies should be designed to assist in the establishment of no-observed-effect levels and to provide evidence of potential short- and long-term hazards, from which an estimate of the chemical’s relative safety can be made.

Studies should be conducted using active constituents, the formulation for which registration is sought, or read-across from a formulation that has similar physicochemical and toxicological properties to the formulation for which registration is sought. These similarities between the two formulations may be due to:

• a common active constituent functional group
• common breakdown products via physical and/or biological processes that result in structurally similar chemicals
• a constant pattern in physicochemical and/or biological properties.

The value of scientific arguments for read-across will be determined based on their merits and reliability.

Details of studies should follow relevant recognised testing guidelines and data reporting. These include, but are not restricted to:

• selection of animal species, housing and feeding conditions, and preparation and randomisation of animals
• a description of study procedure including route of administration, number and characteristics of animals in the main and any interim, satellite or recovery groups; dose selection rationale and dose preparation
• all parameters studied
• the frequency at which parameters were studied
• the duration and frequency of dosing and any recovery period
• the time of administration in relation to the observations and effects observed.

Reports should include detailed results for the individual animals in the studies, together with statistical analyses of results. You should include summary tables or diagrams where these will assist in reviewing data (for example, body weight, haematology, metabolite profile) or where they will permit sets of data to be compared on the same page (for example, those for control and treated animals). Studies should also include summarised reports of histopathological examinations, in tabular form, so that the incidence of observations can be studied in relation to dosage, sex and duration of treatment. You should also provide historical control data, if available.

When undertaking toxicity studies, guidance in toxicology study design can be obtained from the adopted OECD Guidelines for the testing of chemicals, or equivalent recognised test guidelines.

You should include additional toxicological studies on individual metabolites or degradation products in situations where the metabolites or degradation products formed through animal metabolism, photodegradation or other mechanism differ from those identified in mammalian metabolism studies, or a scientific rationale as to why such studies are not necessary. These studies are used to judge which compounds should be included in the residue definition, and may also be used to assess the risk to humans from a toxic degradation product during application.

5.2. Animal testing

Experiments involving animals should be conducted using the minimum number of animals recommended in the adopted OECD Guidelines for the Testing of Chemicals or other recognised test guidelines. Applicants are encouraged to submit data obtained from adopted OECD Guidelines for the Testing of Chemicals (or other recognised test guidelines) in vitro assay systems or alternative methods which use fewer animals according to the ‘3Rs’ principle (reduce, refine, replace).

Each application should contain complete reports of all animal investigations and in vitro studies. These data should cover each of the elements listed under the heading ‘Data elements for a comprehensive Part 3 (toxicology) submission’ that are relevant to the application. You should also provide any available human data.

5.3. Chemistry and manufacture

Applications that include toxicological data should be accompanied by Part 2—Chemistry and manufacture data. This is because details of the chemical and physical properties of the active constituent, the profile of impurities and the constituents of formulations are important in carrying out a complete toxicological evaluation of the product.

Impurities present in an active constituent used in the formulation of a veterinary product may be important both toxicologically and environmentally. Consequently, you should identify any impurity present in the active constituent at a concentration that may be toxicologically significant, in addition to identifying all impurities present in the active constituent at a concentration of one gram per kilogram or more.

Formulation constituents should be clearly identified by name and Chemical Abstracts Service registry number. The use of trade names or proprietary names alone is not acceptable. You should provide all available information relevant to the hazard assessment of non-active constituents used in the product. This information should include, but is not limited to, a safety data sheet for each of the constituents.

For further details, refer to Part 2—Chemistry and manufacture.

5.4. Extrapolation of data

In certain cases, it may be possible to estimate the acute toxicity of a formulation by extrapolation from acute toxicity data on the active constituent (for example, a simple dilution in water, or a tablet formulation in an inert material), or by read-across from a reference product formulation that has similar physicochemical and toxicological properties to the formulation for which registration is sought. Estimates of the potential hazard by extrapolation and read-across should take into consideration the acute toxicity of the active constituent as well as the acute toxicity of the individual non-active constituents. However, data based on the product to be registered is always preferable.

Where you do not provide acute toxicity studies on the proposed product formulation, you should submit a valid scientific argument outlining why you have not provided the data. You should note that if scientific argument is provided in lieu of studies, the minimum recommendation for evaluation is a safety data sheet for each constituent in the product formulation.

Further, where two or more active constituents are formulated together in a novel combination (that is, a hazard profile has not been previously established), toxicity studies should be performed with the formulated product as outlined in ‘Toxicity of mixtures’, to investigate the possibility of synergism or potentiation. Alternatively, in the absence of data, you should provide a scientific argument to address the toxicity.

5.5. Approval of a new source of an approved active constituent

Registrants may apply for approval of a new source of an approved active constituent. This may require a full assessment, a limited assessment or no assessment, depending on the impurity profile of the active constituent from the new source. If you apply for approval of a new source of an approved active constituent which is not equivalent to the approved source in terms of its impurity profile, toxicological data should be provided.

The data elements that you should provide for a limited toxicology assessment are:

• acute oral and dermal toxicity studies
• two in vitro genotoxicity studies (as outlined below under the heading ‘Genotoxicity studies’.

These studies should be conducted on the source of active constituent containing the listed impurities (or on the listed impurities) to demonstrate equivalence.

Scientific argument for not undertaking studies on a new source of active constituent can be submitted for consideration. The argument should follow a stepwise approach:

1. determination of the hazard profile of the newly identified or toxicologically significant impurities; that is, whether the impurities are classified for human health effects on Safe Work Australia’s Hazardous Substances Information System
2. consideration of information from acceptable toxicology databases and literature searches providing information on the hazard profile of the impurities, or data on both the impurity and the structurally similar chemical if read-across is proposed
3. supportive quantitative structure–activity relationship evidence derived using Deductive Estimation of Risk from Existing Knowledge (DEREK) software, as a prediction of the toxicity of the impurity and structurally similar chemical if read-across is proposed.

Information from this stepwise approach should support the proposed scientific argument that equivalence is demonstrated and testing is not relevant. The regulatory value of scientific arguments will be determined on their merits and reliability.

5.6. Guideline for domestic veterinary chemical products

Poisoning by domestic veterinary chemical products can, and does, occur. Domestic veterinary chemical products should be relatively harmless or capable of causing only mild illness if accidental poisoning occurs.

The following guidelines, when applied to experimental animal data, should reduce the hazard of domestic veterinary chemical products. Appropriate consideration of inherent toxicity, formulation, packaging and labelling can reduce the hazard and risk to users, and especially young children. These guidelines need to be considered in the context of other safety measures, such as formulation, product type and innovative packaging.

5.6.1. Acute oral toxicity

Any domestic veterinary chemical product that may be ingested should not be expected to be acutely toxic to a child at doses up to 1500 milligram per kilogram (mg/kg) body weight. Recognising that acute toxicity may reflect a range of adverse effects, the use of the term ‘acutely toxic’ here is intended to mean life-threatening.

The following aspects of acute oral toxicity will determine whether a domestic veterinary product is considered acutely toxic to a child:

• where acute toxicity data on the formulation is available, it would be used to determine whether the value of 1500 milligram per kilogram body weight is not appropriate and may be increased
• whether one or two swallows (approximately 10 gram or 10 millilitre) of the product presents an acutely toxic dose to an infant or small child.

5.6.2. Acute dermal toxicity

A domestic veterinary chemical product should not be acutely toxic at dermal doses up to 2000 milligram per kilogram body weight.

5.6.3. Acute inhalational toxicity

A domestic veterinary chemical product should not be acutely toxic at inhalational concentrations up to 2000 milligram per cubic metre (four-hour exposure) for a gas, 20 milligram per litre (four-hour exposure) for a vapour and 5 milligram per litre (four-hour exposure) for dusts and mists.

5.6.4. Irritancy potential

The irritancy to skin and eyes of domestic veterinary chemical products should be low. The formulation and application methods of a product will be taken into consideration on a case-by-case basis. You should provide relevant information regarding any risk mitigation measures available for the proposed product.

5.6.5. Repeated exposure

Domestic veterinary chemical products should present a low risk from repeated use. For instance, such products should be unlikely to induce irreversible toxicity.

5.6.6. Directions for safe use

Safe use of domestic veterinary chemical products should not require safety equipment that is not readily available to the householder. Safety equipment other than gloves is not considered an appropriate mitigation option for users of domestic veterinary products, because users are not trained in handling hazardous substances and compliance is not expected. Domestic veterinary chemical products may not be supported for domestic use if safety equipment other than gloves is required for their safe use.

5.6.7. First aid directions

The product label affixed to the container and any associated leaflets should carry appropriate first aid directions in the event of poisoning. Veterinary chemical products should not require specific antidotes or aggressive first aid measures.

5.7. Data elements

The data elements for a comprehensive assessment of toxicology data are shown under the heading ‘Data elements for a comprehensive Part 3 (toxicology) submission' below. Unless specified, all studies should be conducted with the active constituent for which approval is sought.

If you believe that a specific data element is not relevant to your application, you should justify the absence of studies by providing a valid scientific argument under the heading for the data element(s) in question. Similarly, a valid scientific argument to justify the absence of acute toxicity studies should be provided under the heading of the data element when read-across is proposed from a formulation that has similar physicochemical and toxicological properties to the product formulation for which registration is sought.

5.7.1. Data elements for a comprehensive Part3 (toxicology) submission

The data elements for a comprehensive assessment of toxicology data are:

• Contents
• Data summary
• Absorption, distribution, metabolism and excretion (toxicokinetics, pharmacokinetics)
• Acute toxicity studies:
  • Studies on the active constituent
  • Studies on the product
• Short-term toxicity studies (repeat dose)
• Sub-chronic toxicity studies (repeat dose)
• Long-term (chronic) toxicity studies (repeat dose):
  • Chronic toxicity studies
  • Carcinogenicity studies
  • Combined chronic toxicity and carcinogenicity studies
• Reproduction studies
• Developmental studies (including developmental neurotoxicity)
• Genotoxicity studies
• Neurotoxicity studies
• Additional studies:
  • toxicity of metabolites and impurities
  • other adverse effects
  • toxicity of mixtures
  • mechanistic studies and mode of action
  • immunotoxicity
• Human toxicological data
• No-observed-effect level
• Acceptable daily intake
• Acute reference dose
• First aid instructions and safety directions
• Toxicological database/bibliography

5.7.1.1. Contents

A table of contents should be provided.

5.7.1.2. Data summary

Your application should include an overall summary of the toxicological information provided in relation to the active constituent or product, as well as rationale for any conclusions made. The summary should contain:

• a brief description of the active constituent or product (including hazard classification and packaging)
• a brief description of the pattern of use of the product. A detailed description of the data elements that you should provide is given in Part 6—Occupational health and safety.

All principal treatment-related changes, such as biochemical and morphological changes observed in the studies should be identified in the data summary, with proper cross-referencing to the detailed data. Where your application claims that:

• findings are not toxicologically significant, you should provide evidence of their reversibility and a scientific argument in support of the proposal. By anticipating such possibilities from early tests, it may be possible to include subgroups for recovery trials in later studies
• findings are not treatment related, you should provide a scientific argument supporting the claim, supported by historical control data if available, preferably from the testing laboratory and by the route of administration tested
• findings are considered to be of low relevance to humans, you should provide a scientific argument based on mechanistic data identifying the mode of action and using a weight-of-evidence approach for the relevance of the identified mode of action to human health based on the Bradford Hill criteria. This approach is contained within the International Programme on Chemical Safety Mode of Action framework for analysing the relevance of a cancer mode of action for humans.

The regulatory value of scientific argument that findings were not toxicologically significant, not treatment related or of low relevance to humans, will be determined on their merits and reliability.

You may use tables as a means of summarising the information. Where studies are cited, they should be cross-referenced in the main body of the application.

If you have submitted metabolism and kinetics data under Part 4, you should summarise these data with argument as to how they relate to relevant aspects of toxicology.

In most cases, the data summary need not exceed two to three pages.

5.7.1.3. Absorption, distribution, metabolism and excretion (toxicokinetics, pharmacokinetics)

You should provide studies examining the absorption, distribution, metabolism and elimination of active constituents in appropriate laboratory animals (see Part 4—Metabolism and kinetics for further details). The route of administration for these studies should be carefully considered, and take into account routes of likely exposure to the active constituent in question.

An investigation of the extent of dermal absorption of the active constituent or product is desirable for risk assessment. In the absence of dermal absorption data, a default value of 100% substance applied to the skin is assumed as a worst case value. Applicants can refine the dermal absorption value by exploring further sources of information to estimate dermal absorption. For instance, the amount considered absorbable may be reduced by an applicant giving consideration to a substance’s specific physicochemical properties; so, for example, if a substance has a molecular weight of greater than 500 and a partition coefficient (log P_ow) less than -1 or greater than 4, the default will be reduced from 100 to 10 per cent dermal absorption.

For dermal absorption studies provided in support of an application, the tested formulation should be identical to, or closely resemble, the product under consideration. The adequacy of this similarity will be determined on a case-by-case basis. Tested concentrations should represent expected human exposure concentrations; for example, the concentration of chemical in the product and the proposed end-use concentration(s) should be tested. Submission of in vitro dermal absorption studies using (1) rat and (2) human skin in conjunction with (3) an in vivo rat dermal study (a ‘triple pack’) is recommended to enable likely human dermal absorption to be estimated. The adequacy of dermal absorption data that does not follow the triple-pack approach will be assessed on a case-by-case basis and may be of reduced value for risk assessment purposes.

You can find further guidance on conducting and interpreting dermal absorption studies in the OECD Guidance notes on dermal absorption.

5.7.1.4. Acute toxicity studies

Acute toxicity studies examine the adverse effects arising from administration of a single oral dose or a single dermal or inhalation exposure of a substance over a specified period or multiple doses given within 24 hours.

To allow assessment of the acute toxicology of a substance, studies in animals should examine the most likely routes and forms of exposure in humans.

Acute oral toxicity studies should be performed in at least one mammalian species. Rats are the preferred rodent species for oral studies unless a species more representative of human toxicity is known. You should also provide acute dermal and inhalation studies in at least one species. For skin and eye irritation studies, rabbits are an acceptable species, but alternatives from adopted OECD guidelines for the testing of chemicals (or other recognised guidelines) to the usual in vivo test may be suitable. In vivo eye irritation tests may not be appropriate in certain circumstances. If you do not believe an eye irritation study is appropriate, you should provide a valid scientific argument as to why these studies should not be included. For example, if the results from a skin irritation study or validated in vitro study demonstrated corrosivity or severe irritation, it is acceptable not to test the product in an eye irritation study, as it is presumed that the product will be corrosive to the eye. Similarly, products with pH extremes of 2 or less, or 11.5 or more are considered corrosive to the eye, unless the acid or alkaline reserve (buffering capacity) of the product suggests otherwise.

A skin sensitisation study is performed to test for possible hypersensitivity reactions to the substance. Guinea pigs are normally used for sensitisation studies. Internationally validated alternative methods, such as the murine local lymph node assay, are also acceptable.

5.7.1.5. Acute toxicity studies (formulated product)

For each new veterinary product, you should submit a ‘six-pack’ of acute toxicological data. This consists of the following studies on the product:

• acute oral toxicity
• acute dermal toxicity
• acute inhalation toxicity
• eye irritation
• skin irritation
• skin sensitisation.

If such data are not available, you should provide valid scientific argument as to why you have not submitted data. In certain circumstances, a toxicological evaluation of the product may be conducted by taking the known toxicological properties of the active constituents and excipients in the formulation and extrapolating these to estimate the acute toxicity of the product. We recommend that you adequately address the reasoning for not providing toxicity studies.

5.7.1.6. Short-term toxicity studies (repeat-dose studies of less than 90 days duration)

Short-term toxicity studies involve multiple administration of a substance for periods of less than 90 days. Such studies provide information on the possible health hazards likely to arise from repeated exposures over a limited period of time.

For classes of chemicals that cause cholinesterase inhibition, short-term oral (gavage) studies in animals, incorporating frequent monitoring of cholinesterase levels, are desirable.

5.7.1.7. Sub-chronic toxicity studies (90 days to less than 12 months)

Sub-chronic toxicity studies are performed to assess possible effects observed in short-term repeated exposure and as preliminary dose range-finding studies before chronic studies are started. They should demonstrate a range of activity, from the no-observed-effect level through to a toxic effect level. Often this range can be encompassed in a single study using one control and three test groups.

Sub-chronic toxicity studies should be performed in two species, a rodent and a non-rodent species. Dogs are the commonly used non-rodent species. Rabbits are not considered an acceptable non-rodent species unless available data suggest that they are more relevant for the prediction of health effects in humans.

5.7.1.8. Long-term (chronic) toxicity studies (12 months or longer)

5.7.1.8.1. Chronic toxicity studies

You should provide long-term (chronic) studies to assess long-term toxic effects (chronic toxicity) that may not be demonstrable in sub-chronic studies (for example, from cumulative toxicity).

Chronic toxicity studies normally consist of long-term, continuous, daily oral administration of the test compound to two species. The use of both a rodent and non-rodent species is desirable to provide an adequate assessment of interspecies variation. Rats and dogs are the preferred species. If you do not provide long-term studies in both a rodent and non-rodent species, we will consider other information you have provided, such as the findings from the sub-chronic studies in rodent and non-rodent species in relation to differences in species sensitivity and target organ toxicity (taking into consideration potential dose-spacing issues). The absence of chronic toxicity studies in both a rodent and non-rodent species may be considered a significant data omission or may require an additional safety factor to be implemented to account for observed differences in species sensitivity.

In chronic toxicity studies, it is desirable to have a dose–response relationship as well as a no-observed-effect level. To this end, normally one control and at least three test groups should be used. The highest dosage should induce a recognisable toxic response without eliciting excessive lethality. At least one dosage level should result in no observed toxic effects. Where a no-observed-effect level is not achieved and the study is identified as the key study for risk assessment purposes and/or establishing an acceptable daily intake value, an additional safety factor may be implemented to account for the uncertainty regarding a lower limit of toxicity.

5.7.1.8.2. Carcinogenicity studies

Carcinogenicity studies are normally performed in two species. Such studies should be regarded as relevant whenever biologically significant residues of the compound or its metabolites occur, or when human exposure to the compound results from the normal use pattern of the compound.

Carcinogenicity testing may not be relevant for an active constituent that is not intended for food-producing use, has a restricted use pattern, and is not an in vivo somatic cell genotoxicant, and where findings in available systemic toxicity data do not raise concerns for carcinogenicity (for example, absence of pre-neoplastic lesions).

Carcinogenicity studies involve administration of the test material, usually in the feed, throughout the major portion of the life span of the species. An adequate number of animals should be included at each dose level to enable suitable statistical evaluation of the results (that is, most of the animals should survive for the duration of the study). It is recommended that rodent species such as rats and mice be used. The use of non-rodent species may be considered when available data suggest that they are more relevant for the prediction of health effects in humans.

You should present historical data describing the normal occurrence of a finding in the particular species and strain of animal in the testing laboratory for the route of administration tested. This assists in deciding whether or not a tumour or lesion is compound related. The submission of historical control data not from the testing laboratory, and/or not by the route of administration that the test used, may be of reduced or no regulatory value.

Where a tumour is considered to be of low relevance to humans, you should provide a supporting scientific argument, based on mechanistic data identifying the mode of action and using a weight-of-evidence approach for the identified mode of action to human health based on the Bradford Hill criteria.

The regulatory value of scientific arguments that tumour findings were of low relevance to humans, will be determined on their merits and reliability.

5.7.1.8.3. Combined chronic toxicity and carcinogenicity studies

A combined chronic toxicity and carcinogenicity study may provide information on the possible chronic and carcinogenic effects likely to arise for a period lasting up to the entire life span of the species. However, careful design is suggested because information for each objective may differ.

You should present historical data describing the normal occurrence of a finding in the particular species and strain of animal in the testing laboratory for the route of administration tested. This assists in deciding whether or not a tumour or lesion is compound related. The submission of historical control data not from the testing laboratory, and/or not by the route of administration that the test used, may be of reduced or no regulatory value.

Where a tumour is considered to be of low relevance to humans, you should provide a supporting scientific argument, based on mechanistic data identifying the mode of action and using a weight-of-evidence approach for the identified mode of action to human health based on the Bradford Hill criteria.

The regulatory value of scientific arguments that tumour findings were of low relevance to humans, will be determined on their merits and reliability.

5.7.1.9. Reproduction studies

Reproduction studies involve the administration of a substance over one or more generations (multi-generation studies) to provide information on the effects of the substance on male and female reproductive systems, including gonadal function, the oestrus cycle, mating behaviour, conception, gestation, parturition, lactation, and weaning, and the growth and development of the offspring.

Such studies may also provide information about the effects of the test substance on neonatal morbidity, mortality, and preliminary data on prenatal and postnatal developmental toxicity, and serve as a guide for subsequent tests. These studies should be conducted with at least three dose groups and a concurrent control group, and would normally be conducted using rodents, preferably rats.

If other species are used, justification should be given and the test parameters should be modified as appropriate.

5.7.1.10. Developmental studies

Developmental studies involve administration of a substance to pregnant animals over a specified period of gestation (organogenesis) to provide information on prenatal exposure on the pregnant test animal and on the developing foetus, and may include assessment of maternal effects as well as death, structural anomalies and abnormalities, or altered growth in the foetus. Functional deficits, although an important part of development, are generally assessed in reproduction and developmental neurotoxicity studies.

Developmental toxicity studies should be performed in a rodent and non-rodent species. Rats are the preferred rodent species and rabbits are the preferred non-rodent species. You should provide justification if another species is used.

5.7.1.11. Genotoxicity studies

It is now known that some substances can cause changes to the genetic material. These changes may involve a single gene, or whole chromosomes (structural and/or numerical), and damage to deoxyribonucleic acid (DNA) via effects such as unscheduled DNA synthesis, DNA strand breaks, DNA adduct formation or mitotic recombination. A set of well-validated tests able to detect different classes of genetic toxicants will demonstrate the potential of a compound to induce genetic damage in humans. Tests (i) and (ii) described below should be conducted in the first instance:

1. a test designed to demonstrate the induction of point mutations (base-pair substitution and frameshift) in a microbial assay (for example, salmonella reverse mutation test), with and without the use of appropriate metabolic activation systems
2. a test designed to demonstrate the production of chromosome damage in an in vitro mammalian cell assay (for example, Chinese hamster ovary assay), with and without the use of appropriate metabolic activation systems.

An in vivo test is also recommended.

If (i) or (ii) are positive, two of three tests described below under (iii), (iv) and (v) should be carried out in rodents (rats or mice) in order to characterise the genotoxic potential in vivo in somatic cells:

3. a test designed to demonstrate the production of cytogenetic damage (for example, micronuclei) in the bone marrow or other proliferative cells of intact animals
4. a test designed to demonstrate genotoxic damage, involving other than cytogenetic endpoints (for example, unscheduled DNA synthesis or P32-post-labelling adduct formation) and preferably in a suspect or known target tissue for the substance
5. a test designed to demonstrate mutations in transgenic rats or mice that have transgenes containing reported genes for the detection of various types of mutations in somatic tissues.

If (iii), (iv) or (v) are positive, a test described below under (vi), (vii) or (viii) should be carried out in rodents (rats, mice or Chinese hamsters) in order to better characterise the genotoxic potential in vivo in germ cells:

6. a test designed to demonstrate a dominant lethal event in a germ cell that does not cause dysfunction of the gamete, but which is lethal to the fertilised egg or developing embryo
7. a test designated to demonstrate the production of chromosome aberrations in spermatogonial cells
8. a test designed to demonstrate mutations in transgenic rats or mice that have transgenes containing reporter genes for the detection of various types of mutations through the germline.

5.7.1.12. Neurotoxicity studies

A neurotoxic effect is an adverse change in the structure or function of the nervous system (central or peripheral) that results from exposure to a substance. A neurotoxic effect may arise in offspring from exposure of the mother during pregnancy and lactation. Adverse changes may result from single or repeat exposure to a substance.

Tests should be designed to detect or characterise major neurobehavioural and neuropathological effects in test animals. While behavioural effects—even in the absence of morphological changes—can reflect an adverse impact on the organism, not all behavioural changes are specific to the nervous system. Therefore, any changes observed should be evaluated in conjunction with correlative histopathological, haematological or biochemical data as well as data on other types of systemic toxicity. A developmental and delayed neurotoxicity study should be considered based on all the available information. A developmental neurotoxicity study should be conducted when neurotoxicity is observed in acute or repeat dose studies. Delayed neurotoxicity studies (acute and repeat dose) should be conducted if the substance is an organophosphorous compound.

Relevant testing (acute, sub-chronic, developmental and delayed neurotoxicity) should be conducted in accordance with appropriate test guidelines.

5.7.1.13. Additional studies

5.7.1.13.1. Toxicity of metabolites and impurities

Although it is recognised that toxicity studies usually examine the toxicity of the active constituent, impurities or metabolites may contribute significantly to the toxicity of the compound. In general, studies employing the active constituent provide an overall estimate of toxicity of the parent compound and its metabolites. However, where metabolites produced in target animals are significantly different from those produced in laboratory animals, you should provide toxicity studies on those metabolites. Submitted data should allow an assessment of what metabolites should be included in the residue definition for risk assessment purposes.

All impurities with concentrations of one gram per kilogram or greater (or those impurities with concentrations of less than one gram per kilogram that are toxicologically significant) in the active constituent should be identified and, where necessary, subjected to appropriate toxicological studies or a scientific argument (see ‘Approval of a new source of an approved active constituent’ above for information on scientific arguments).

If you will be providing toxicological studies, you should provide at least one acute oral and one in vitro genotoxicity study (as outlined under the heading ‘Genotoxicity studies’). These studies should be conducted on the listed impurities and metabolites and if these are demonstrated to be more hazardous than the active constituent, they may be identified as toxicologically relevant for risk assessment purposes.

5.7.1.13.2. Other adverse effects

Individual compounds that show specific toxicological effects (for example, immunotoxicity, neurotoxicity) during normal repeat dose testing should be further investigated using appropriate tests for the particular abnormalities induced to enable definitive hazard characterisation to be established. Similarly, new compounds that belong to chemical classes known to produce particular toxicological effects should also be tested appropriately; for example, delayed neurotoxicity with organophosphorous insecticides. In the absence of such information, the toxicity profile of a compound may be deemed incomplete. The regulatory impact of an incomplete toxicity profile will be determined on a case-by-case basis.

5.7.1.13.3. Toxicity of mixtures

Where two or more active constituents are formulated together in a novel combination (that is, a hazard profile has not been previously established), toxicity studies should be performed with the formulated product to investigate the possibility of synergism or potentiation. In the absence of data, you should provide a scientific argument so that a determination of the regulatory value of the argument can be considered. When undertaking toxicological studies, acute toxicity studies are usually sufficient for this purpose (that is, acute oral, dermal and inhalational toxicity studies, skin and eye irritation studies, and a skin sensitisation study).

Where synergism or potentiation is found, further studies or scientific argument may be necessary to clarify its toxicological significance.

5.7.1.13.4. Mechanistic studies and mode of action

Mechanistic studies may be undertaken to supplement data obtained from standard studies conducted in accordance with the adopted OECD guidelines for the testing of chemicals, or other recognised test guidelines, so as to explain the process involved in, or responsible for, an observed toxicological finding. Together, the data may identify the overall mode of action by which a substance produces its toxicological effect, from a subcellular level through to histopathological changes.

When proposing that the observed toxicological effect is of low relevance to humans, you should provide a scientific argument based on the available data, identifying the mode of action and using a weight-of-evidence approach for the relevance of the identified mode of action to human health based on the Bradford Hill criteria.

5.7.1.13.5. Immunotoxicity

An immunotoxic effect is an adverse effect on the components and/or function of the immune system from exposure to a substance resulting from either direct or indirect actions reflecting either permanent or reversible toxicity.

While OECD test guidelines for short-term, sub-chronic and chronic toxicity studies may provide data to give an indication of immunological effects, there is no specific OECD test guideline to determine functional immunotoxicity. If such studies provide an indication of an immunological effect, you should consider further testing to investigate immunotoxicity using appropriate tests. The US Environmental Protection Agency has a functional immunotoxicity test guideline designed to evaluate the immunosuppressive potential of a substance (OPPTS 870.7800).

5.7.1.14. Human toxicological data

You should provide all available information relating to human experience with the substance. The information may arise as a result of voluntary intake, occupational exposure during the manufacture of the substance, worker exposure during use, or reports of accidental poisoning.

You should include studies relating to occupational and/or worker exposure in Occupational health and safety (Part 6) of your application.

5.7.1.15. No-observed adverse effect level

The no-observed adverse effect level is the highest dose of a substance at which there is no detectable adverse alteration of morphology, functional capacity, growth, development, or lifespan of the target organism under defined conditions of exposure compared to those observed in control (untreated) animals, and which are observed or measured at higher dose levels used in the study.

The no-observed adverse effect level is expressed in milligrams of substance per kilogram of body weight per day (mg/kg bw/day) or, in a feeding study, as parts per million (ppm) in food. For feeding studies, conversion to mg/kg bw/day should be made, calculated from substance intake by measured or estimated food intake over the study period.

Where the test substance is given in feed, and problems with the stability of the test compound occur, the feed should be analysed at frequent intervals.

5.7.1.16. Lowest-observed adverse effect level

The lowest-observed adverse effect level is the lowest dose of a substance at which there is a detectable adverse alteration of morphology, functional capacity, growth, development, or lifespan of the target organism under defined conditions of exposure compared to those observed in normal (untreated) animals.

The lowest-observed-effect level is expressed in milligrams of substance per kilogram of body weight per day (mg/kg bw/day) or, in a feeding study, as parts per million (ppm) in food. For feeding studies, conversion to mg/kg bw/day should be made, and where problems with the stability of the test compound occur in feed, the feed should be analysed at frequent intervals.

5.7.1.17. Acceptable daily intake for humans (toxicological)

The acceptable daily intake for humans is the level of intake of a substance that can be ingested daily over an entire lifetime without appreciable risk to health on the basis of the available information at the time of evaluation. It is expressed in milligrams of the substance per kilogram of body weight per day (mg/kg bw/day).

For this purpose, ‘without appreciable risk’ means that adverse effects are unlikely to result even after a lifetime of exposure. The acceptable daily intake is intended to give a guide to the maximum amount of a substance that can be ingested daily in the food without appreciable risk to the consumer. Accordingly, the figure is derived as far as possible from feeding studies in animals.

You can view a list of current acceptable daily intakes on the APVMA website.

5.7.1.18. Acceptable daily intake for humans (microbiological)

The acceptable daily intake for humans is the level of intake of antibiotics with antimicrobial activity that enter the human colon and can be ingested daily over an entire lifetime without appreciable risk to health on the basis of the available information at the time of evaluation. An ADI is established on the basis of microbiological data and expressed in milligrams of the substance per kilogram of body weight per day (mg/kg bw/day).

For this purpose, ‘without appreciable risk’ means that antimicrobial effects on human intestinal flora of health concern are unlikely to result even after a lifetime of exposure. The acceptable daily intake is intended to give a guide to the maximum amount of an antimicrobial substance that can be ingested daily in the food without appreciable risk to the consumer. Accordingly, the figure is derived from in vitro or in vivo (oral route) studies investigating disruption of the colonization barrier and increases in the population(s) of resistant bacteria.

Guidance on studies to evaluate the safety of antibiotics is provided in VICH Guideline no. 36.

5.7.1.19. Acute reference dose (toxicological)

The acute reference dose of a substance is an estimate of the amount of a substance in food and/or drinking water, expressed in milligrams of substance per kilogram of body weight (mg/kg bw), that can be ingested over a short period of time, usually in one meal or during one day, without appreciable health risk to the consumer, on the basis of all known facts at the time of the evaluation. For some substances, an acute reference dose may not be necessary because the substance is not considered to cause appreciable acute risk after a single dose or exposure (that is, 24 hours or less).

You can view a list of current acute reference doses on the APVMA website.

5.7.1.20. First aid instructions and safety directions

You may propose first aid instructions and safety directions applicable for each formulation. You should use standard phrases as published in the APVMA's First aid instructions and safety directions handbook.

You should note, however, that first aid instructions and safety directions are established by the APVMA, taking into account the hazard profile of an active constituent or chemical product, as well as the occupational and/or residential risks associated with the proposed use patterns for the product.

5.7.1.21. Toxicological database and bibliography

Every application (including supplementary applications) should include a toxicological database comprising a full bibliography of all studies provided in the application. Every application (including supplementary applications) that contains toxicological data should include a list of all studies on the active constituent and/or chemical product. You should clearly identify studies lodged as part of the application.

For each listed study, you should provide the following information:

• identity and the concentration or purity of the material tested (for example, active constituent, product)
• type of test (for example, acute oral study, two-year dietary study)
• species and strain of animal used
• study laboratory and names of authors
• study sponsor
• good laboratory practice status (including certification where applicable)
• title of the report, report number and date of report
• date the study was submitted in Australia
• location in the application (volume, page number).

6. Poison schedules

You may include a scheduling proposal when submitting a toxicology data package. Your scheduling proposal will be assessed against the scheduling factors described on the Therapeutic Goods Administration website. The scheduling factors ensure that public health objectives are consistently met when making scheduling decisions.

The schedules accompanying the states’ and territories’ Poisons Acts listing the various poisons under categories that are based on the recommendations published in the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP, produced by the Australian Government Department of Health). Active constituents intended for veterinary use and veterinary chemical products generally fall into one of the following categories:

6.1. Schedule 4

Substances that should, in the public interest, be restricted to medical, dental or veterinary prescription or supply.

6.2. Schedule 5

Substances with a low potential for causing harm, the extent of which can be reduced through the use of appropriate packaging with simple warnings and safety directions on the label.

6.3. Schedule 6

Substances with a moderate potential for causing harm, the extent of which can be reduced through the use of distinctive packaging with strong warnings and safety directions on the label.

6.4. Schedule 7

Substances with a high potential for causing harm at low exposure and which require special precautions during manufacture, handling or use. These poisons should be available only to specialised or authorised users who have the skills necessary to handle them safely. Special regulations restricting their availability, possession, storage or use may apply.

6.5. Schedule 8

Substances which should be available for use but require restriction of manufacture, supply, distribution, possession and use to reduce abuse, misuse and physical or psychological dependence.

6.6. Appendix B

Those substances that do not require control by scheduling because of low toxicity, or where other factors suggest that the potential public health risk would be minimal, are listed in Appendix B of the SUSMP. This appendix should be read in conjunction with Appendix A (general exemptions).

7. References

We have provided below details for current editions at the time of publication. You should always ensure that you obtain the most recent edition of any publication.

Australian Government Department of Health, Standard for the Uniform Scheduling of Medicines and Poisons, online publication.

Organisation for Economic Co-operation and Development, OECD guidelines for the testing of chemicals, online publication, OECD.

Australian Pesticides and Veterinary Medicines Authority, Acceptable daily intakes for agricultural and veterinary chemicals.

Australian Pesticides and Veterinary Medicines Authority, Acute reference doses for agricultural and veterinary chemicals.

Australian Pesticides and Veterinary Medicines Authority, First aid instructions and safety directions handbook.

VICH 2004, Studies to evaluate the safety of residues of veterinary drugs in human food: reproduction testing, VICH Guideline no. 22,International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

VICH 2004, Studies to evaluate the safety or residues of veterinary drugs in human food: genotoxicity testing, VICH Guideline no. 23, International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

VICH 2002, Studies to evaluate the safety of residues of veterinary drugs in human food: carcinogenicity testing, VICH Guideline no. 28, International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

VICH 2004, Studies to evaluate the safety of residues of veterinary drugs in human food: repeat-dose (90-days) toxicity testing, VICH Guideline no. 31, International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

VICH 2004, Studies to evaluate the safety of residues of veterinary drugs in human food: developmental toxicity testing, VICH Guideline no. 32, International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

VICH 2009, Studies to evaluate the safety of residues of veterinary drugs in human food: general approach to testing, VICH Guideline no. 33, International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

VICH 2012. Studies to evaluate the safety of residues of veterinary drugs in human food: General approach to establish a microbiological ADI. VICH Guideline no. 36, International Cooperation on Harmonisation of Technical Requirements of Veterinary Medicinal Products.

World Health Organization/Food and Agriculture Organization Joint Meeting on Pesticide Residues 2004, ‘General considerations: Guidance on the establishment of acute reference doses’, in Pesticide Residues in Food, FAO Plant Production and Protection Paper, vol.178, pp. 3–9.