Pharmacokinetics and pharmacodynamics of tezosentan, an intravenous dual endothelin receptor antagonist, following chronic infusion in healthy subjects

Aims The purpose of this study was to investigate the tolerability, pharmacokinetics, and pharmacodynamics of tezosentan, air intravenous dual endothelia receptor antagonist, during chronic infusions in healthy male subjects. Methods Tezosentan was infused at a rate of 100 mg h(-1) for 6 h (study A, six subjects) and at a rate of 5 mg h(-1) for 72 h (study B, eight subjects). Both studies had a randomized, placebo-controlled, double-blind design. Tolerability and safety were monitored by the recording of vital signs, ECG, adverse events and clinical laboratory parameters. Blood samples were collected frequently for pharmacokinetic determinations and measurement of plasma endothelin-1 concentrations. Results In both studies tezosentan was well tolerated with headache the most frequently reported adverse event (incidence of 75-100% for tezosentan and 50% for placebo). Plasma concentrations of tezosentan rapidly approached steady state (3000 and 125 ng ml(-1) in study A and B, respectively) and did not change upon prolonged infusion. A two-compartment model could describe its pharmacokinetic profile. The half-lives of the two disposition phases were approximately 0.10 and 3.3 h. Endothelin-1 concentrations increased rapidly 11- and 2-fold compared with pre-dose values in study A and B, respectively, during infusion of tezosentan and did not change during the 73 h infusion. Conclusions On the basis of these results, dose finding studies with tezosentan in acute heart failure call be initiated in the dose range 5-100 mg h(-1).