The dose of HALDOL Decanoate 50 or HALDOL Decanoate 100 should be expressed in terms of its haloperidol content. The starting dose of haloperidol decanoate should be based on the patient's age, clinical history, physical condition, and response to previous antipsychotic therapy. The preferred approach to determining the minimum effective dose is to begin with lower initial doses and to adjust the dose upward as needed. For patients previously maintained on low doses of antipsychotics (. up to the equivalent of 10 mg/day oral haloperidol), it is recommended that the initial dose of haloperidol decanoate be 10–15 times the previous daily dose in oral haloperidol equivalents; limited clinical experience suggests that lower initial doses may be adequate.
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.
The intravenous route is not FDA approved and is generally not recommended except when no other alternatives are available. Intravenous administration appears to be associated with a higher risk of QT prolongation and torsade de pointes (TdP) than other forms of administration. The manufacturer recommends ECG monitoring for QT prolongation and arrhythmias if IV administration is required. A dose in the range of 1 to 5 mg IV has been suggested, with the dose being repeated at 30 to 60 minute intervals, if needed. A maximum IV dose has not been established. The lowest effective dose should be used in conjunction with conversion to oral therapy as soon as possible.