Pharmacokinetic parameters of trapidil (an antagonist of platelet derived growth factor) were evaluated in 12 healthy male subjects (study I) and in a group of 10 patients with liver cirrhosis (Child B) and five control subjects, respectively (study II). 2. Investigations were carried out after a single dose trapidil (200 mg) and at steady state after application of 200 mg trapidil three times daily for 5 days (study 1) or 4 days (study II). 3. Study I: The concentration-time curves of the terminal elimination phase of trapidil exhibited a slight convexity which might reflect nonlinear kinetics. The AUC of trapidil obtained after the first dose (20.5 [+/- 7.0 s.d.] micrograms ml-1 h) was markedly higher than the AUC determined at steady state (13.2 [+/- 3.8 s.d.] micrograms ml-1 h), the non-parametric 90% confidence intervals of the ratio day 5/day 1 was 0.58-0.73 (point estimator 0.64). 4. Study II: AUC averaged (21.4 [+/- 9.1 s.d.] micrograms ml-1 h) in controls and (34.4 [+/- 14.9 s.d.] micrograms ml-1 h) in cirrhotic patients. The 90% confidence intervals for the difference group 1 vs group 2 was 0.95-2.97 (point estimator 1.48, P = 0.066). At steady state, AUC averaged (13.7 [+/- 5.7 s.d.] micrograms ml-1 h) in controls and (20.8 [+/- 6.8 s.d.] micrograms ml-1 h) in cirrhotic patients (90% confidence intervals group 1 vs group 2: 0.88-2.20 [point estimator 1.45, P = 0.05]). As seen in study I, the AUC of trapidil obtained after the first dose was markedly higher than the AUC determined at steady state, the non-parametric 90% confidence intervals of the ratio day 5/day 1 was 0.48-0.84 (point estimator 0.66) in control subjects and 0.54-0.72 (point estimator 0.64) in cirrhotic patients, respectively. 5. An inverse correlation was seen between the results of the monoethylglycinxilidid (MEGX)-test and the AUC of trapidil (single dose: r = -0.516, P = 0.048; steady state: r = -0.548, P = 0.042). 6. Results of study I and study II indicate an autoinduction of trapidil metabolism after repeated oral doses. Although trapidil elimination is decreased in patients with liver cirrhosis (study II), the elimination half-life at steady state is relatively short (2.4 [+/- 1.1 s.d.] h) and therefore should prevent cumulation of trapidil even in cirrhotic patients.
