Eltoprazine. HCl belongs to a new class of psychotropic drug, the serenics. The dose-proportionality and pharmacokinetics of eltoprazine HCl has been investigated after single oral doses of 5, 10, 20 mg (18 subjects) and 30 mg (12 subjects) in a partly randomized, cross-over design. Eltoprazine was well tolerated and there were no relevant changes in safety parameters. All subjects showed irregular plasma-concentration-time profiles, some subjects demonstrating secondary peaks. The mean half-life was calculated to be about 6.5 h. The renal excretion of eltoprazine was characterized by net tubular secretion. AUC, peak plasma concentrations and the amount excreted unchanged in the urine were linearly related to the dose. Renal clearance and t1/2 were independent of dose. Thus, eltoprazine HCl was well tolerated orally and exhibited a linear pharmacokinetic profile.