Effects of amlodipine on the oral bioavailability of cephalexin and cefuroxime axetil in healthy volunteers.

In this study, the authors compared the effects of amlodipine (AML) on the bioavailability of cephalexin (LEX) and cefuroxime axetil (CXM). Twenty-four healthy men were randomized to 4 treatments according to a crossover design with a 14-day washout. After an overnight fast, they were administered orally LEX 500 mg alone, LEX 500 mg 2 hours after oral administration of AML 5 mg, CXM 500 mg alone, and CXM 500 mg 2 hours after oral administration of AML 5 mg. All participants completed the whole study without side effects being observed. Pharmacokinetic data were analyzed by noncompartmental modeling with WinNonlin software. The geometric mean (GM) ratios were 1.38 (90% confidence interval [CI], 1.32-1.45) for the area under the concentration-time curve (AUC) for LEX and 1.27 (1.18-1.36) for the maximum concentration of drug in serum (C(max)) for LEX followed by AML versus alone. In contrast, no significant differences were found in the pharmacokinetic parameters of CXM between treatments (P < .05). They authors conclude that AML possesses an enhancement effect in β-lactam antibiotic bioavailability (in this case, LEX), and this interaction may be specific to the peptidomimetic β-lactam antibiotics.