A pharmacokinetic study of cicletanine, a new class of antihypertensive drugs was performed in ten healthy volunteers after administration of 50 mg single oral dose. Cicletanine plasma and urine concentrations were measured using the HPLC technique. The main pharmacokinetic parameters were estimated applying a non-compartmental approach. The half-life ranged between 4.76 to 17.76 h; the mean oral and renal clearance were 7.3 +/- 2.5 l/h and 0.026 +/- 0.012 l/h, respectively. The urinary excretion of the product ranged between 37.5 and 64.6% of the administered dose, the amount of unchanged drug being negligible (0.4 +/- 0.3%). Both metabolic conjugation pathways glucuronidation and sulphation occurred in a similar extent 23.7 +/- 6.7% and 23.0 +/- 7% respectively. The overall pharmacokinetic parameters obtained in this study agree with those previously reported after the administration of higher doses (75-300 mg) and is in favour of a linear pharmacokinetic behaviour of cicletanine over the dose range of 50 mg to 300 mg.