Methazole chemical review

In 1995, the then National Drugs and Poisons Scheduling Committee (NDPSC) found that new toxicological data for methazole had revealed dose-related increases in the incidence of cataracts in the offspring of rat dams dosed with methazole. In response to this new information, the NDPSC rescheduled methazole from Schedule 6 to Schedule 7 of the Standard for the Uniform Scheduling of Drugs and Poisons (now the Standard for the Uniform Scheduling of Medicines and Poisons). Schedule 7 compounds are categorised as toxic and must have the signal heading ‘Dangerous Poison’ on the label.

The primary registrant, Sandoz, voluntarily withdrew its products containing methazole and ceased marketing them in 1993. Sandoz did not renew its methazole product registrations, and the remaining amount of stock in the marketplace was considered to be negligible by 1996.

In July 1995, prompted by the NDPSC’s regulatory decision, the APVMA began a special review of methazole based on the toxicological concerns and to consolidate the earlier regulatory action.

The APVMA completed the special review of methazole in February 1996 but did not publish a final report, as the primary registrant had withdrawn all products before the completion of the review. Based on the new toxicological information, the APVMA was not satisfied that the continued use of methazole would not pose an undue hazard to human health.

In the report, the APVMA recommended:

• cancelling the active constituent approval, with effect from 31 March 1996
• cancelling all product registrations, with effect from 31 March 1996
• cancelling the MRLs for methazole, with effect from 31 March 1996.

The APVMA’s concerns about methazole remain and it will not consider the registration of any product containing methazole unless all the concerns identified in the review are fully addressed.

No products containing methazole are currently registered for use in Australia.