Pharmacokinetics of Haloperidol Decanoate in Rats

Plasma levels of haloperidol decanoate and haloperidol after intramuscular administration of haloperidol decanoate in rats showed good fits with a multi-compartment model which was constituted by combination of 2-compartment models for the disposition of haloperidol and for its ester decanoate through the process of hydrolysis of the ester. Calculated parameters indicated that most of intramuscularly administered haloperidol decanoate is absorbed in blood after hydrolysis to haloperidol and the absorption is rate-limiting. Regional lymph node levels suggested that the intramuscularly administered ester was absorbed via the lymphatic system where the hydrolysis to haloperidol probably occurred. Thus, slow entrance and hydrolysis of haloperidol decanoate in the lymphatic system was considered to be the cause of sustained plasma levels of the active principle after intramuscular administration of haloperidol decanoate.