Alaproclate, a specific inhibitor of neuronal serotonin re-uptake, was given to 12 patients with dementia of Alzheimer type. The drug was rapidly absorbed and an elimination half-life of 7.1 +/- 0.9 h (+/- SD, n = 8) was calculated. Plasma protein binding for alaproclate was 82 +/- 1%. Two weeks of repeated administration produced plasma concentrations of alaproclate similar to those predicted from a single dose. The pharmacological effect of the drug was demonstrated by an inhibition of serotonin uptake in the patients' platelets and a reduction of the serotonin concentration in blood. Global rating of clinical efficacy showed a positive effect of alaproclate in five of the patients, mainly regarding emotional functions.