A suppository formulation of the 5HT1 agonist sumatriptan could prove an important therapeutic option in migraine patients who dislike or poorly tolerate injectable therapy and where oral tablet administration is unsuitable because of severe migraine-related vomiting. Two independent double-blind, randomized clinical studies were conducted to evaluate the safety, tolerability and pharmacokinetics of sumatriptan suppositories following ascending single doses (four different dose levels) and multiple doses. In the four-period, crossover, single-dose study, 24 healthy male subjects were randomized to receive a suppository containing 12.5, 25, 50, or 100 mg on separate occasions 3-14 days apart. The suppositories were generally well tolerated; transient asthenia, drowsiness, and headache were the most frequently reported adverse events, and these were not dose-related. Peak plasma concentrations (Cmax) of sumatriptan were proportional to dose from 25 to 100 mg; area under the plasma concentration-time curve (AUC infinity) values were proportional to dose except at the highest doses, when they were greater than those predicted from lower doses. For all doses, the tmax of sumatriptan occurred within 2.5 h, and the t1/2 was approximately 2 h. In the two-period, placebo-controlled, crossover, repeat-dose study, 12 healthy adult male subjects were randomized to receive either a 50-mg sumatriptan suppository or placebo suppository, administered rectally twice a day, for 11 doses (5 1/2 days). Adverse events were no more frequent with sumatriptan than with placebo, and stool guaiac, rectal examinations, and physical examinations remained normal. No significant differences were noted between Day 1 and Day 6 values in the AUC, Cmax, time of peak serum concentration (tmax), elimination half-life (t 1/2), fraction of the dose excreted in the urine (fe), or renal clearance (Clr) of sumatriptan or its pharmacologically inactive indole acetic acid metabolite. Serum metabolite concentrations were two to three-fold higher than corresponding sumatriptan concentrations. No clinically significant accumulation of sumatriptan or its metabolite occurred. Overall, these studies show that sumatriptan administration via a suppository formulation is well tolerated, allows rapid absorption of sumatriptan, results in sumatriptan Cmax values that are proportional to dose from 25 to 100 mg, and is not associated with accumulation of sumatriptan or its metabolite.