THE RELATIVE BIOAVAILABILITY OF 2 MARKETED CONTROLLED-RELEASE DILTIAZEM DOSAGE FORMS AT STEADY-STATE IN HEALTHY-VOLUNTEERS

This study was conducted to determine the relative bioavailability of Dilacor(TM) XR capsules compared to Cardizem(R) CD capsules at both lo w (180 mg d(-1)) and high (540 mg d(-1)) dose levels. Trough and seria l plasma samples were obtained and pharmacokinetic parameters were cal culated from the steady state concentration-time profiles. Mean steady state plasma diltiazem concentrations (AUC(ss)(0-24)) of Dilacor XR w ere 19% and 26% lower than those of Cardizem CD for the 180 mg d(-1) a nd 540 mg d(-1) dose levels, respectively. In addition, Dilacor XR had lower mean C-max,C-ss, T-max,T-ss, C-min,C-ss, and trough values than Cardizem CD with percentage differences ranging from 17% to 29%. The variability (%CV) in the data from the Dilacor XR treatments was highe r for each calculated pharmacokinetic parameter compared to the Cardiz em CD treatments. The %CV for Dilacor XR ranged from 34% to 104% while the %CV for Cardizem CD ranged from 21% to 49%. From these results, i t may be concluded that Dilacor XR is not bioequivalent to Cardizem CD at steady state doses of 180 mg d(-1) and 540 mg d(-1).