Interaction potential and tolerability of the coadministration of cilostazol and aspirin.
OBJECTIVE
This study evaluated the effects of repeated oral drug administration with cilostazol alone and with aspirin (acetylsalicylic acid) on platelet aggregation, coagulation and bleeding time as well as the cilostazol-aspirin pharmacokinetic interaction in healthy males.


METHODS
This was a randomised, double-blind, placebo-controlled, crossover study. Participants received either cilostazol 100 mg or placebo twice a day for 10 days; aspirin 325 mg/day was coadministered for the last 5 days. After a 14-day washout period, participants received the alternative treatment.


METHODS
12 healthy male volunteers were enrolled.


METHODS
Differences in bleeding times, platelet aggregation, prothrombin time (PT) and activated partial thromboplastin time (aPTT) between cilostazol with aspirin and cilostazol alone. Noncompartmental pharmacokinetic parameters were determined for each study participant.


RESULTS
Cilostazol, with or without aspirin, caused no changes in PT, aPTT or bleeding time. There was a 23 to 35% increase in inhibition of ADP-induced ex vivo platelet aggregation by cilostazol plus aspirin when compared with aspirin alone. There was no additive or synergistic effect on arachidonic acid-induced platelet aggregation. Statistically significant but clinically insignificant increases in the area under the plasma concentration-time curve to the last measurable plasma concentration and trough concentrations of cilostazol and its metabolites (OPC-13015 and OPC-13213) occurred after aspirin coadministration, with no differences observed in the maximum plasma concentration Drug-related adverse events were generally mild, the most frequent being headache.


CONCLUSIONS
Cilostazol and aspirin coadministration did not cause clinically significant changes in PT, aPTT, bleeding time, platelet aggregation or plasma concentrations of cilostazol and its 2 active metabolites. Cilostazol was generally well tolerated with or without aspirin.
Mallikaarjun
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Department of Clinical Pharmacokinetics/Pharmacodynamics & Metabolism, Otsuka America Pharmaceutical, Inc., Rockville, MD 20850, USA. steveb@mocr.oapi.com
Forbes
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Bramer
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D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D019540:Area Under Curve; D001241:Aspirin / Q000494:pharmacology*; D001760:Bleeding Time; D000077407:Cilostazol; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004347:Drug Interactions; D004361:Drug Tolerance; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects; D011517:Prothrombin Time; D013777:Tetrazoles / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D013777:Tetrazoles; D014665:Vasodilator Agents; D000077407:Cilostazol; D001241:Aspirin