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Pharmacokinetics of Generic, Trade HIV Drugs Differ

Formulations tested in Malawian population

THURSDAY, Jan. 4 (HealthDay News) -- The pharmacokinetics and bioequivalence of generic and trade versions of a triple HIV-drug formulation are not identical, according to a study conducted in HIV-infected patients from Malawi. The findings are published in the Jan. 2 issue of AIDS.

Angela D.M. Kashuba, Pharm.D., of the University of North Carolina in Chapel Hill, N.C., and colleagues compared the pharmacokinetics and bioequivalence of generic and trade versions of stavudine (40 mg twice daily), lamivudine (150 mg twice daily), and nevirapine (200 mg twice daily) in 12 HIV-infected patients from Malawi in an open-label, crossover study. Subjects had been taking Triomune-40 TM, and pharmacokinetic measurements were taken after each formulation was consumed for at least 21 days.

The researchers found that the geometric mean ratio for generic:trade formulations for maximum plasma concentration (C-max) was 1.4 for stavudine, 1.1 for lamivudine and 0.9 for nevirapine. The corresponding geometric mean ratios for the area under the curve (0-8 hours) were 1.1, 1.0, and 0.9, respectively. Bioequivalence had been defined as when the 90 percent confidence interval for these two numbers was 0.8-1.25. For both formulations, nevirapine exposure was higher than had been reported for Western HIV-infected patients, the authors note.

"Although exposures were similar, Triomune did not meet the strict definition of bioequivalence for these drugs. Patients taking Triomune had notably higher stavudine C-max values," Kashuba and colleagues conclude. "Antiretroviral pharmacokinetics and bioequivalence of generic formulations should be evaluated in the populations in which they are being used."

The study was funded by a program sponsored by the U.S. National Institutes of Health.

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