Article date: September 2000
By: Andrew L. Masica, Nkechi E. Azie, D. Craig Brater, Stephen D. Hall, David R. Jones, in Volume 50, Issue 3, pages 273-276
Aims To study whether intravenous diltiazem, a calcium channel blocker commonly prescribed for hypertension and stable angina, is an inhibitor of the CYP3A enzymes by using oral lovastatin, an HMG Co‐A reductase inhibitor, as a substrate.
Methods Ten healthy volunteers were studied in a randomized two‐way crossover design. The two arms were 1) administration of a 20 mg dosage of lovastatin orally and 2) administration of a 20 mg dosage of lovastatin orally 1 h after an intravenous loading dosage and constant infusion of diltiazem. Blood samples were collected up to 25 h in order to quantify lovastatin and diltiazem concentrations in the separated serum. Lovastatin and diltiazem concentrations were quantified by GC‐MS and h.p.l.c., respectively.
Results Intravenous diltiazem did not significantly affect the oral AUC, Cmax, t½, or tmax of lovastatin.
Conclusions These data suggest that the interaction of lovastatin with diltiazem does not occur systemically and is primarily a first‐pass effect. Thus, drug interactions with diltiazem may become evident when a patient is moved from intravenous to oral dosing.
DOI: 10.1046/j.1365-2125.2000.00249.x
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