Abstract

After a 1-month placebo run-in phase, 27 patients with proven peripheral arterial obstructive disease participated in a double blind placebo controlled study and were divided in 3 groups, receiving either placebo, ridogrel 300 mg b.i.d. (a combined thromboxane synthase and receptor blocking agent) or a combination of ridogrel 300 mg b.i.d. and ketanserin 20 mg t.i.d. (a 5-HT2 serotonergic receptor antagonist) for a period of 1 month. In both active treatment groups, serum levels of thromboxane B2 decreased significantly to 3% of baseline. The levels of 6-keto-prostaglandin F1 alpha and prostaglandin F2 alpha increased two- to three-fold and levels of prostaglandin E2 6 times. Platelet aggregation induced by collagen and by U 46619, a thromboxane A2 mimetic, were significantly inhibited by both treatment regimen. Template bleeding times were significantly prolonged but plasma fibrinogen levels and the activated partial thromboplastin time were not affected with the active treatments. No such changes were seen with placebo. An inhibition of the serotonin-induced platelet aggregation was only seen in the ketanserin-treated group. In a 3-month open follow-up period during combined treatment with ridogrel and ketanserin in 22 patients, the effects on platelet function and prostanoids were maintained. The total duration of the walking distance on a treadmill improved significantly from 323 +/- 53 seconds to 399 +/- 48 seconds and the onset of claudication pain improved significantly from 121 +/- 29 seconds to 212 +/- 44 seconds, whereas the maximal drop of the post-exercise ankle/arm pressure gradient markedly and significantly improved from a control value of 0.38 +/- 0.05 to 0.51 +/- 0.05. These findings suggest that a combination of ridogrel and ketanserin may be of therapeutic value in the treatment of intermittent claudication.