Effects of ketoprofen and ibuprofen on platelet aggregation and prostanoid formation in man.

Objective: In the present randomized, fourway crossover study we determined the effects of two oral doses each of ketoprofen and ibuprofen on platelet aggregation and prostanoid formation in man.
Methods: Twelve healthy female volunteers received for 2 consecutive days, followed by a 5-day drug-free interval, one of the following: ketoprofen 3 x 25 mg per day, or ketoprofen 3 x 50 mg per day, or ibuprofen 3 x 200 mg per day, or ibuprofen 3 x 400 mg per day. The response criteria, determined before and on the 2nd day of each treatment period, were: maximal platelet aggregation in response to 1.0 mmol.l-1 arachidonic acid measured by the method of Born and Cross, thromboxane B2 (TXB2) concentration in platelet-rich plasma after aggregation measured by radioimmunoassay, and PGE-M, the index metabolite of total body prostaglandin E2 (PGE2) production, assessed by gas chromatography/tandem mass spectrometry using 18O2-PGE-M as internal standard.
Results: Platelet aggregation was significantly reduced by ketoprofen 3 x 25 mg per day (-57%) and ketoprofen 3 x 50 mg per day (-85%) as compared to control, whereas ibuprofen 3 x 200 mg per day (-3%) and ibuprofen 3 x 400 mg per day (-22%) had no significant effects. TXB2 synthesis was significantly decreased by ketoprofen 3 x 25 mg per day (-72%), ketoprofen 3 x 50 mg per day (-97%) and ibuprofen 3 x 400 mg per day (-48%) as compared to control; ibuprofen 3 x 200 mg per day did not reduce TXB2 formation significantly (-23%). All four treatments reduced 24-h urinary excretion of PGE-M significantly in the range of -39% (ketoprofen 3 x 25 mg per day) to -53% (ibuprofen 3 x 400 mg per day) without significant differences between treatments.
Conclusion: Our data show that both ketoprofen dosages were more effective in inhibition of platelet aggregation and platelet thromboxane synthesis than ibuprofen in low or high dosage. Total body synthesis of the E-prostaglandins was inhibited by all drug schedules without significant differences between treatments.