Different pharmacokinetic parameters of neuroleptic drugs, absorption rate, biological half-life, systemic availability, and linear kinetics, are discussed in relation to dosing frequency and dose. Special attention is paid to the serum level profiles of two injectable preparations for acute treatment - zuclopenthixol dihydrochloride in aqueous solution and zuclopenthixol acetate in Viscoleo. Data are presented on a depot preparation of zuclopenthixol, the decanoic ester in Viscoleo, given at four-week intervals. A direct comparison of the three injectable preparations of zuclopenthixol shows that the acetate in oil can be considered as a retard preparation. The pharmacokinetics places it between the aqueous solution and the depot preparation, but, being closest to the aqueous solution, it is a good alternative to this preparation for the treatment of acute psychosis.