The effect of prolonged treatment with sulphinpyrazone on thromboxane A2 and prostacyclin in man

Effects of ischaemic heart disease, Crohn's disease and antimicrobial therapy on the pharmacokinetics of sulphinpyrazone

The renewed interest in sulphinpyrazone in recent years has arisen from its potential to inhibit platelet aggregation. In vivo much of the activity is probably due to the thioether or sulphide metabolite which has a greater potency and a longer half-life than the parent compound. The sulphide metabolite is formed exclusively by the gut microflora in man. The pharmacokinetics of sulphinpyrazone (200 mg orally) have been studied, with particular attention to the formation of the sulphide metabolite, in groups of patients who might be expected to show abnormal formation of this active metabolite due to altered delivery of the drug to the lower gut or altered gut flora. Five patients studied 1 month after a myocardial infarction did not differ markedly from young, normal volunteers with respect to either sulphinpyrazone or its metabolite. Crohn's disease in the quiescent phase did not significantly alter the pharmacokinetics or metabolism of the drug, but 1 patient who had undergone a hemicolectomy formed negligible concentrations of the active metabolite. Antimicrobial therapy produced highly variable results with almost complete suppression of sulphide formation in some subjects but no apparent effect in others.

A pharmacokinetic and platelet function study of the combined administration of metoprolol and sulfinpyrazone to healthy volunteers

In a double-blind study on healthy subjects who underwent three 3-week periods of treatment with metoprolol (M) + sulfinpyrazone (S), M + placebo, and S + placebo, pharmacokinetics and plasma levels of M were not affected by concurrent administration of S. Analysis of variance change-over demonstrated a significant difference between treatments only for serum uric acid levels. Analysis of post-treatment and baseline data within each treatment showed: decreased platelet count by M, lowered serum 6-keto PGF1 alpha by all three treatments, decreased serum TXB2 generation and arachidonic acid-induced platelet aggregation by S + M. No negative interaction between S + M was found.

Effects of fenflumizole on aggregation ex vivo of human platelets and formation of thromboxane B2 and 6-keto-prostaglandin-F1 alpha

Fenflumizole (2-(2,4-difluorophenyl)-4,5-bis(4-methoxyphenyl)imidazole), a new non-steroidal anti-inflammatory drug, was given to healthy subjects in single oral doses of 0.1, 1 and 2 mg/kg. The effect of the drug was followed for up to 8 h by repeated tests of arachidonic acid-induced platelet aggregation and was related to its concomitant plasma concentration. Fenflumizole reversibly inhibited platelet aggregation and the degree of inhibition was found to be linearly correlated with the log plasma concentration. There was depression of the formation of thromboxane B2 and 6-keto-prostaglandin F1 alpha (the stable metabolites of thromboxane A2 and prostacyclin) in clotted whole blood measured by radioimmunoassay after fenflumizole 1 mg/kg. This effect was directly related to the concentration of the drug in plasma, the maximum effect being reached at fenflumizole concentrations greater than 200 ng/ml. EC50-values for inhibition of the formation of thromboxane B2 and 6-keto-prostaglandin F1 alpha were approximately 20 and 40 ng/ml, respectively. The results suggest that orally administered fenflumizole is a potent inhibitor of platelet aggregation and prostanoid formation.