PHENYLBUTAZONE (PBZ), also known as ‘bute’, is a NSAID authorised to treat horses suffering from musculoskeletal disorders such as rheumatoid and arthritic diseases and to relieve them from the associated pain.
An assessment of PBZ by The Committee for Medicinal Products for Veterinary Use (CVMP) (European Medicines Agency 1997) found that the main health risks to the consumer were blood dyscrasias and the genotoxic/carcinogenic potential for which no thresholds could be identified and so no maximum residue limits could be established. As a consequence of this assessment, PBZ is not permitted for use in any animal destined for the food chain. The risks were reconfirmed more recently in a joint statement by the European Food Safety Authority and European Medicines Agency (2013). In addition to the EU, PBZ is banned from use in food production animals in most other countries, including the USA, Canada and Japan.