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CIBA-GEIGY’s TEGRETOL AND GENERIC CARBAMAZEPINE ARE "EQUIVALENT"

Executive Summary

CIBA-GEIGY's TEGRETOL AND GENERIC CARBAMAZEPINE ARE "EQUIVALENT" in clinical efficacy, according to a study conducted at the Bowman Gray School of Medicine, Wake Forest University. "In one of the first studies ever comparing a brandname drug with its generic 'equivalent' in clinical effectiveness, the generic drug indeed turned out to be equivalent," researchers announced in an Oct. 16 release. The three-year, double-blind study involved a comparison of the effectiveness of Ciba-Geigy's carbamazepine and a generic version, Lemmon's Epitol, in controlling epileptic seizures. "Coded dose packages of one round white pill and one pink oblong pill were given to each patient, one active and one a placebo," the release says. The 40 patients involved in the trial received one of the active drugs for three months and then were switched to the other drug. Ciba and Lemmon contributed their carbamazepine products and placebo forms of the drugs. Lemmon initiated the study because of concerns that generic epilepsy drugs may not be interchangeable with the brandname product and that switching from one to another may lead to breakthrough seizures ("The Pink Sheet" Dec. 11, p. 3). This concern has been reflected in decisions by states to place generic carbamazepine products on negative formularies. For example, Florida's medical board voted to do so last year, although the generic subsequently was removed from the negative formulary following a hearing officer's decision that the state's actions were "arbitrary or capricious." The study also addresses claims made by some brandname drug manufacturers that brandname products are superior to their generic versions. Parke-Davis contracted with Boston University to conduct a bioequivalence study of its anticonvulsant Dilantin with Bolar's generic phenytoin, and the study reportedly demonstrated that Bolar's drug was not bioequivalent to Dilantin. On the other hand, FDA determined that an additional analysis indicated that the study did not demonstrate inequivalence. However, Bolar subsequently recalled its phenytoin product because it could not assure bioequivalence in light of serious questions regarding the reliability of information supporting the ANDA. On Oct. 16, the Bowman Gray research team presented the study's results at the American Neurological Association meeting in Atlanta. "The number of seizures that occurred despite the presence of the drug averaged 0.22 per day on Tegretol and 0.25 per day on Epitol -- statistically the same," the release states. "The study showed carbamazepine [from] these two manufacturers were equivalent in clinical effectiveness." The Bowman Gray study also determined that "the average variation in blood levels for Epitol and Tegretol was within the allowable 20% difference." FDA allows blood levels of a generic drug to vary up to plus or minus 20% when compared to the brandname drug. The research team was headed by J. Kiffin Penry, professor of neurology, and Karen Oles, associate professor of neurology. In the release, Penry pointed out that the study cannot be applied to the generic carbamazepine products made by five other manufacturers. "I can't say they aren't equivalent, but we haven't done the study to show they are equivalent," he stated.
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