Mark G. Eller

Comparison of the Pharmacokinetics of Two Nicotine Transdermal Systems: Nicoderm and Habitrol

This randomized, crossover study compared the nicotine and cotinine pharmacokinetic parameters and plasma concentration profiles of two different nicotine transdermal products: Nicoderm (Alza, Palo Alto, CA; and Marion Merrell Dow, Kansas City, MO) and Habitrol (Basel Pharmaceuticals, Summit, NJ). The two treatments were randomly assigned to each of 24 male smokers and worn for 24 hours each day for 5 days, with a 6‐day washout between treatments. Plasma nicotine and cotinine concentrations were measured on day 1 and day 5 of each treatment. Mean delivered dose differed significantly between products, and the two products were not bioequivalent. The Nicoderm system provided higher mean plasma nicotine concentrations, particularly during the first 8 hours after system application. The mean steady state Cmax, AUC, and degree of fluctuation (DF) values were significantly greater for the Nicoderm system than for Habitrol. The mean nicotine tmax value for the Nicoderm system was significantly shorter (P < .001) than that for Habitrol (2.7 versus 8.6 hours). Steady state cotinine AUC values and plasma concentrations were significantly lower for Habitrol than for the Nicoderm system. The incidence of adverse events was similar for both products.

Pharmacokinetics of Terfenadine in Healthy Elderly Subjects

The pharmacokinetics of the terfenadine active metabolite, metabolite I, was examined in ten healthy elderly adults and ten younger adults after single‐dose oral administration of 120‐mg terfenadine. All subjects successfully completed the study without reporting sedation or other adverse events. Absorption was rapid in both the young and elderly. The mean Cmax was the same for both groups, 501 ng/mL, and occurred at 2.3 hours in the young subjects and 2.5 hours in elderly subjects. However, the apparent clearance was reduced by about 25% in the elderly. After correcting clearance for bodyweight, this difference was not statistically significant.

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

This study was conducted to determine the relative bioavailability of Dilacor XR capsules compared to Cardizem CD capsules at both low (180 mg d-1) and high (540 mg d-1) dose levels. Trough and serial plasma samples were obtained and pharmacokinetic parameters were calculated from the steady state concentration-time profiles. Mean steady state plasma diltiazem concentrations (AUCss(0-24)) of Dilacor XR were 19% and 26% lower than those of Cardizem CD for the 180 mg d-1 and 540 mg d-1 dose levels, respectively. In addition, Dilacor XR had lower mean Cmax,ss, Tmax,ss, Cmin,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 higher for each calculated pharmacokinetic parameter compared to the Cardizem 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, it 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.