Proof of the linearity of the pharmacokinetics of alinidine in man

Summary The pharmacokinetics of alinidine was investigated in two groups of volunteers: Group I (N=5) received on two different occasions single doses of¹⁴C-labelled drug given orally (40 mg) or intravenously (10 mg); Group II (N=6) received single oral doses 10, 30 or 90 mg dissolved in 20 ml water. The samples from Group I were analysed by two different and independent methods (RIA and counting total radioactivity). The results obtained by the two methods were identical, since the compound was not metabolized. The plasma concentrations and renal excretion data obtained from both groups were individually fitted to an open three compartment model. Independent of the route of administration and of the doses given, similar pharmacokinetic parameters were calculated for each group and each trial. The half lives of the distribution and elimination phases were t_1/2: 36–41 s, t_1/2 : 9.9–11.1 min and t_1/2: 2.7–3.8 h. There was a linear relationship between the dose administered and the resulting areas under the plasma concentration curves (AUC). Following a lag period (=0.19–0.22 h), the peak plasma concentration was reached 0.6–1.2 h after oral administration. Oral alinidine was 100% bioavailable.