WEDNESDAY, Dec. 5 (HealthDay News) -- The U.S. Food and Drug Administration has concluded that generic Budeprion XL 300 mg (extended-release bupropion hydrochloride, manufactured by Impax Laboratories and distributed by Teva Pharmaceuticals) cannot be considered therapeutically equivalent to the brand-name product, according to a perspective piece published online Dec. 5 in the New England Journal of Medicine.
Noting that Budeprion XL 300 mg was approved based on extrapolation of the results of a bioequivalence study of Budeprion XL 150 mg and Wellbutrin XL 150 mg, Janet Woodcock, M.D., from the Center for Drug Evaluation and Research at the FDA in Rockville, Md., and colleagues reviewed new data providing direct comparative pharmacokinetic analyses of Budeprion XL 300 mg with Wellbutrin XL 300 mg. They conducted a bioequivalence study involving 24 healthy fasting volunteers in a single-dose crossover design.
The researchers found that the extent of bupropion absorption for the generic product was 86 percent of that of the brand-name product, and that the mean peak plasma concentration observed after Budeprion XL 300 mg administration was only 75 percent of that observed after administration of Wellbutrin XL 300 mg. In certain participants, the maximum plasma concentration and area under the plasma concentration curve for Budeprion XL were less than 40 percent of those for Wellbutrin. The time to peak drug concentration in the blood was shorter for Budeprion XL (four hours) than for Wellbutrin XL (five hours).
"We at the FDA are therefore changing our bioequivalence recommendations for extended-release bupropion products and have asked other manufacturers of 300-mg extended-release bupropion products to conduct additional bioequivalence studies," the authors write. "We do not believe that the results of the FDA study should cause concern regarding the overall reliability of the agency's approval process for generic drugs, including the use of extrapolation, when scientifically appropriate."
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