Prior to the adoption of the cylinder plate method as the official method for detection of penicillin in milk products, states were using the Disc Assay procedure. This resulted in situations where the state's results were negative for inhibitory substances while FDA's test using the unofficial cylinder method were positive for penicillin. Regulatory action was not considered appropriate in these circumstances.
Since that time FDA adopted the Cylinder Plate Method as the official assay for the detection of penicillin in milk and milk products. FDA's Division of Federal-State Relations informed the State Health Officers, State Agriculture Commissioners, State Dairy Officials, and State Laboratory Directors of our decision to adopt the more sensitive cylinder plate method as official and requested that they proceed as soon as possible to adopt that method as their official analytical assay for the detection of penicillin in milk and milk products. Some states have complied with this request. Since the adoption of the Cylinder Plate Method we have consistently advised inquirers that while they may use other methods as preliminary tests, products found to be positive by the official method would be considered actionable.
Milk and milk products containing penicillin are adulterated within the meaning of Section 402(a)(2)(D) of the Federal Food, Drug, and Cosmetic Act in that they contain a new animal drug which is unsafe. Such milk and milk products may be subjected to reconditioning however, any reconditioning process will be considered and approved on a case by case basis by FDA. Products will be released subject to analysis by FDA using the most sensitive method (official method) for penicillin detection.
Milk and milk products containing penicillin which have satisfactorily passed through a reconditioning process and have been released by FDA may be used for human food or as a component of other food products.