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ANDA APPROVALS BASED ON LOCAL ABSORPTION ARE WITHIN FDA’s DISCRETION

Executive Summary

ANDA APPROVALS BASED ON LOCAL ABSORPTION ARE WITHIN FDA's DISCRETION, the agency declared in a June 29 letter to Schering-Plough. The letter asserts FDA's authority to approve ANDAs for all nonsystemically absorbed drugs in response to Schering's attempt to bar approvals of such products, including generic versions of the company's inhaled albuterol Proventil and the clotrimazole products Lotrimin, Lotrimin AF, Lotrisone, and the Gyne-Lotrimin. Schering "cites no legislative history, and FDA is aware of none suggesting that Congress had any intention of excluding nonsystemically absorbed drugs...from ANDA eligibility," the agency asserted. FDA observed that the nonsystemically absorbed products represent "a large class of drugs for which FDA had been granting ANDAs under its existing bioavailability and bioequivalence regulations for over 15 years." Congress established a mandatory definition of bioequivalence but did not seek to exclude other definitions of bioequivalence, FDA maintained. "Even if that section [of the statute] does not encompass nonsystemically absorbed drugs, Congress has not removed FDA's discretion to adopt other scientifically supportable definitions of bioequivalence that may be applicable to nonsystemically absorbed drugs," the agency commented. The definition of bioequivalence in the statute reads that a generic drug "shall be considered bioequivalent [if] the rate and extent of absorption of the drug do not show a significant difference from the rate and extent of absorption of the listed drug." The definition of bioequivalence is not exclusive to systemically absorbed drugs, FDA argued. "FDA believes that the reference to bioequivalence in [the statute] applies to both systemically and locally absorbed drugs." Schering "assumes incorrectly, that the statutory references to absorption must mean 'systemic absorption,"' FDA stated, adding that "it is well-established that drugs may be either locally or systemically absorbed." Continuing, the agency remarked that "nothing about this definition requires that the absorption result in the transit to the systemic circulation." In its May 23 petition, Schering contended that no adequate method exists to measure directly the rate and extent of local absorption in humans. FDA countered that "nothing in the statutory references to bioequivalence requires that bioequivalence studies include direct measurement of the rate and extent of absorption." FDA asserted: "On the contrary, the statute expressly authorizes indirect measurements of bioequivalence," citing the provision in the statute for in vitro studies. Schering submitted its first petition on December 4, one day before the expiration of the patents for albuterol and clotrimazole ("The Pink Sheet" Dec. 11, T&G-12). "Certainly a more timely filing could have been attempted," FDA remarked. Schering subsequently filed new arguments and data on the importance of local absorption for topical generic products ("The Pink Sheet" May 28, T&G-14). FDA said that a further response to the May 23 petition will be forthcoming.
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