Relative bioavailability and effects of a high fat meal on single dose cilostazol pharmacokinetics

The objectives of this research were to (1) assess the relative bioavailability following administration of a 100 mg cilostazol suspension versus 100 mg tablet; (2) assess dosage form equivalency (2 x 50 mg compared with 1 x 100 mg); (3) compare the relative bioavailability following a single 50 mg dose of cilostazol administered as an ethanolic solution versus a 50 mg tablet; and (4) determine the effects of high fat diet on the pharmacokinetics of cilostazol following a single dose of 100 mg cilostazol in the fed or fasted state. Results were compiled from 3 separate studies to address these objectives.

All studies involved healthy adult males receiving single oral doses of cilostazol in the fed or fasted state. The fed state consisted of administering cilostazol after ingestion of a high fat meal. One study compared the relative bioavailability of 100 mg suspension and 2 x 50 mg tablet versus 100 mg tablet in a randomised crossover design. The study involving administration of a 50 mg cilostazol ethanolic solution was a single treatment study. The effects of food on the pharmacokinetics of cilostazol after administration of 100 mg cilostazol in the fed or fasted state as well as the pharmacokinetic profile following administration of a single 50 mg oral dose of cilostazol were assessed in a randomised crossover design.

All participants were healthy nonsmoking males aged between 19 and 48 years whose bodyweight was within 15% of ideal bodyweight.

Noncompartmental pharmacokinetic parameters were determined for each study participant.

The area under the plasma concentration-time curve (AUC) parameters were within the 80 to 125% criterion for bioequivalence for the cilostazol and its primary metabolite, OPC-13015. The maximum observed plasma concentrations (Cmax) for these formulations were not equivalent and indicated that the absorption of cilostazol from a suspension is more rapid than from a tablet. The apparent terminal half-lives (t1/2z) of cilostazol and OPC-13015 were shorter after administration of the suspension compared with the tablet. Cmax and AUC following administration of a single 50 mg cilostazol tablet were approximately 80% of that from the same dose administered as an ethanolic solution. The t1/2z of cilostazol decreased from 15.5 hours after a tablet to 2.5 hours after an ethanolic solution. Upon coadministration with a high fat meal, the Cmax of cilostazol increased 90% and AUC infinity increased 25% (p < 0.05). The t1/2z decreased from 15.1 +/- 14.5 hours (mean +/- SD) in the fasted state to 5.4 +/- 2.0 hours in the fed state. Single oral doses of 50 and 100 mg cilostazol were well tolerated.

The relative bioavailability of the 100 mg cilostazol tablet versus an oral 100 mg cilostazol suspension is 100%. The 2 x 50 mg and 1 x 100 mg tablets are considered to be bioequivalent. The absorption following administration of 50 mg cilostazol ethanolic solution is faster and appears to be greater than that after administration of the 50 mg tablet. Coadministration of food increases the rate and extent of cilostazol absorption. The oral pharmacokinetics of cilostazol and metabolites are absorption-rate limited. The significant differences in the t1/2z observed when comparing cilostazol tablet, suspension, and solution as well as the effects of food suggest 'flip-flop' pharmacokinetics.