DRUGS LACK THERAPEUTICAL EQUIVALENCE IF THEY ARE NOT BIOEQUIVALENT

DRUGS LACK THERAPEUTICAL EQUIVALENCE IF THEY ARE NOT BIOEQUIVALENT or pharmaceutically equivalent, Washington attorney Jonah Shacknai (Royer Shacknai & Mehle) maintained in a Dec. 4 letter to FDA. Responding to a letter by Rep. Waxman (D-Calif.), who commented on Shacknai citizen petitions ("The Pink Sheet" Nov. 10, p. 16), the Washington lawyer said: "FDA's regulations make it clear that a drug will not be deemed to be "therapeutically equivalent" to a listed drug unless it is both 'pharmaceutically equivalent' and 'bioequivalent' to that drug."

In publishing the "Orange Book," FDA said two drugs are not pharmaceutically equivalent if their active ingredients, salts or esters, dosage forms or compendial standards differ, Shacknai pointed out. Therefore, products that vary by as little as 1% in amount of active ingredient are not therapeutically equivalent because they are not pharmaceutically equivalent, he contended. "Similarly, a drug product which is approved for a dosage schedule which is shorter than that of the listed drug would not be 'bioequivalent' to the listed drug over the full length of the dosage schedule for which the listed drug is approved."

Such products "should not be rated therapeutically equivalent" to the listed drug "because such differences may, with certain drugs, pose substantial safety and effectiveness questions," Shacknai maintained.

Furthermore, he implied Waxman's letter was an attempt to modify the intent of the ANDA/patent law. "It is well settled that post-enactment interpretations of legislation by legislators cannot change the legislative intent expressed prior to passage of the act," Shacknai said. Quoting an opinion from National School of Aeronautics, Inc. v. U.S., he added: "Statements made by a legislator after enactment of a statute and not part of the records of the legislative body are entitled to little or no weight at all."

Shacknai also submitted a separate Dec. 4 letter to FDA in responding to comments on its petitions by the Generic Pharmaceutical Industry Association (GPIA). The association's arguments that the ANDA/patent act does not apply retroactively to previous therapeutic equivalence ratings nor address therapeutic equivalence in any way "are largely irrelevant to the points raised by the" citizen petitions, Shacknai said. Therapeutic equivalence ratings should be applied consistently for public health reasons. Consequently, a drug approved under ANDA-suitability procedures "will not meet FDA's criteria for both 'pharmaceutical equivalence' and 'bioequivalence' to the listed drug . . . and therefore may not carry an 'A' rating in the 'Orange Book,'" he said. "Rather it must carry no rating, as is the case with 'pharmaceutical alternatives,' or carry a 'B' rating, as is the case with drugs which are not bioequivalent."