Influence of piroxicam coadministration on pharmacodynamic parameters and the plasma concentration/effect relationship of recombinant hirudin (CGP 39393).

Recombinant hirudins are currently under investigation for use in myocardial infarction and unstable angina. In this study the influence of piroxicam on the pharmacodynamics and pharmacokinetics of a recombinant hirudin preparation (CGP 39393) administered intravenously was determined. Twelve healthy, male volunteers received piroxicam 10 mg and matching placebo once daily for 12 days according to a double-blind, randomised cross-over design. On the 12th day, the dose of piroxicam was followed by a 6-hour infusion of hirudin 0.1 mg.kg-1.h-1. Plasma concentrations and urinary excretion of hirudin and repeated measurements of the activated partial thromboplastin time (APTT), bleeding time and platelet adhesion index were assessed up to 24 h after the start of the infusion. The maximum APTT was 83 s (placebo) and 84 s (piroxicam), 3 to 4 h after the start of the infusion, and was comparable on both study days. The AUD0-24 (APTT) came to 913 s.h.kg-1 under placebo and it was slightly increased to 1,017 s.h.kg-1 after piroxicam; the 95%- confidence interval according to MOSES ranged from 0.97 to 1.24, and the point estimator was 1.10. Bleeding time was significantly prolonged from 290 s under placebo to 345 s under piroxicam before the start of the infusion of hirudin. No further prolongation was found during or after the infusion. No change was observed in the platelet adhesion index. Responsiveness parameters according to a sigmoidal Emax-model were obtained from the hirudin-plasma concentration/effect (i.e. APTT-prolongation)-curves after placebo and piroxicam.(ABSTRACT TRUNCATED AT 250 WORDS)