Effect of concomitant colestipol hydrochloride administration on the bioavailability of diltiazem from immediate- and sustained-release formulations
Article first published online: 27 NOV 2002
Copyright © 2002 John Wiley & Sons, Ltd.
Biopharmaceutics & Drug Disposition
Volume 23, Issue 9, pages 369–377, December 2002
How to Cite
Turner, S. W., Jungbluth, G. L. and Knuth, D. W. (2002), Effect of concomitant colestipol hydrochloride administration on the bioavailability of diltiazem from immediate- and sustained-release formulations. Biopharm. Drug Dispos., 23: 369–377. doi: 10.1002/bdd.330
- Issue published online: 27 NOV 2002
- Article first published online: 27 NOV 2002
- Manuscript Accepted: 19 JUN 2002
- Manuscript Revised: 12 JUN 2002
- Manuscript Received: 14 JAN 2002
- drug interaction;
Effects of concomitant colestipol administration on plasma concentrations of diltiazem and desacetyldiltiazem from immediate-release (IR) and sustained-release (SR) formulations were assessed in two studies. In the first study, 12 subjects received 120-mg diltiazem hydrochloride (diltiazem) SR capsules or 120-mg diltiazem IR tablets administered alone and in combination with colestipol hydrochloride (colestipol). Following concomitant administration of SR diltiazem with colestipol, AUC0–∞ and Cmax, respectively, were 22 and 36% less, and were 27 and 33% lower for IR diltiazem. In the second study, subjects received 120-mg diltiazem SR capsules at staggered times, without colestipol, 1 h prior to or 4 h following multiple doses of colestipol. A 17% decrease in AUC0–∞ was observed when diltiazem was taken 1 h before colestipol was given, and a 22% decrease when diltiazem was taken 4 h after colestipol, relative to diltiazem SR alone. Cmax values were similarly decreased. Results from these two studies show that colestipol can cause a significant decrease in diltiazem absorption from both IR and SR dosage forms. Staggering the administration of colestipol and diltiazem SR did not blunt this effect, indicating that concomitant administration of diltiazem and colestipol should be used with caution, and that the efficacy of diltiazem should be monitored to assure adequate dosing. Copyright © 2002 John Wiley & Sons, Ltd.