Thirty patients with chronic schizophrenia received oral haloperidol and haloperidol decanoate in a two-phase open study. In the first phase, patients were stabilized on haloperidol tablets for 2 weeks, then maintained on a constant daily dose for 2 more weeks. They were then switched to haloperidol decanoate for the second phase. Patients were first stabilized on a monthly dose of haloperidol decanoate and then received this dose for 5 consecutive months. Haloperidol decanoate, administered in monthly injections at to 15 times the daily oral dose, was at least as efficacious as oral haloperidol in controlling the symptoms of schizophrenia. There were no serious adverse reactions to either drug. Blood samples were taken from 22 patients during both the oral and the decanoate phases and analyzed for steady state haloperidol concentrations. These determinations demonstrate that the release of haloperidol with the decanoate form is sustained throughout the 4-week dosing interval. Lower plasma drug concentrations were observed during decanoate treatment than during oral treatment. Despite these lower plasma concentrations, patients remained stable on both drug regimens. This finding suggests that haloperidol decanoate injected every 4 weeks can provide control of psychotic symptoms at least as effectively as daily oral haloperidol.
There are no well controlled studies with Haldol (haloperidol) in pregnant women. There are reports, however, of cases of limb malformations observed following maternal use of Haldol along with other drugs which have suspected teratogenic potential during the first trimester of pregnancy. Causal relationships were not established in these cases. Since such experience does not exclude the possibility of fetal damage due to Haldol, this drug should be used during pregnancy or in women likely to become pregnant only if the benefit clearly justifies a potential risk to the fetus.