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Prolixin Decanoate Dosage

Generic name: fluphenazine decanoate
Dosage form: Injection, USP
Drug class: Phenothiazine antipsychotics

Medically reviewed by Last updated on Jul 31, 2023.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Prolixin Decanoate (Fluphenazine Decanoate Injection) may be given intramuscularly or subcutaneously. A dry syringe and needle of at least 21 gauge should be used. Use of a wet needle or syringe may cause the solution to become cloudy.

To begin therapy with Prolixin Decanoate the following regimens are suggested:

For most patients, a dose of 12.5 to 25 mg (0.5 to 1 mL) may be given to initiate therapy. The onset of action generally appears between 24 and 72 hours after injection and the effects of the drug on psychotic symptoms becomes significant within 48 to 96 hours. Subsequent injections and the dosage interval are determined in accordance with the patient’s response. When administered as maintenance therapy, a single injection may be effective in controlling schizophrenic symptoms up to four weeks or longer. The response to a single dose has been found to last as long as six weeks in a few patients on maintenance therapy.

It may be advisable that patients who have no history of taking phenothiazines should be treated initially with a shorter-acting form of fluphenazine (see HOW SUPPLIED section for the availability of the shorter-acting fluphenazine hydrochloride dosage forms) before administering the decanoate to determine the patient’s response to fluphenazine and to establish appropriate dosage. For psychotic patients who have been stabilized on a fixed daily dosage of Prolixin Tablets (Fluphenazine Hydrochloride Tablets USP), Prolixin Elixir (Fluphenazine Hydrochloride Elixir USP), or Prolixin Oral Concentrate (Fluphenazine Hydrochloride Oral Solution), conversion of therapy from these short-acting oral forms to the long-acting injectable Prolixin Decanoate may be indicated.

Appropriate dosage of Prolixin Decanoate (Fluphenazine Decanoate Injection) should be individualized for each patient and responses carefully monitored. No precise formula can be given to convert to use of Prolixin Decanoate; however, a controlled multicentered study,* in patients receiving oral doses from 5 to 60 mg fluphenazine hydrochloride daily, showed that 20 mg fluphenazine hydrochloride daily was equivalent to 25 mg (1 mL) Prolixin Decanoate every three weeks. This represents an approximate conversion ratio of 0.5 mL (12.5 mg) of decanoate every three weeks for every 10 mg of fluphenazine hydrochloride daily.

*The Initiation of Long-Term Pharmacotherapy in Schizophrenia: Dosage and Side Effect Comparisons Between Oral and Depot Fluphenazine; N.R. Schooler; Pharmakopsych. 9:159-169, 1976.

Once conversion to Prolixin Decanoate is made, careful clinical monitoring of the patient and appropriate dosage adjustment should be made at the time of each injection.

Severely agitated patients may be treated initially with a rapid-acting phenothiazine compound such as Prolixin Injection (Fluphenazine Hydrochloride Injection USP—see package insert accompanying that product for complete information). When acute symptoms have subsided, 25 mg (1 mL) of Prolixin Decanoate may be administered; subsequent dosage is adjusted as necessary.

“Poor risk” patients (those with known hypersensitivity to phenothiazines, or with disorders that predispose to undue reactions): Therapy may be initiated cautiously with oral or parenteral fluphenazine hydrochloride (see package inserts accompanying these products for complete information). When the pharmacologic effects and an appropriate dosage are apparent, an equivalent dose of Prolixin Decanoate may be administered. Subsequent dosage adjustments are made in accordance with the response of the patient.

The optimal amount of the drug and the frequency of administration must be determined for each patient, since dosage requirements have been found to vary with clinical circumstances as well as with individual response to the drug.

Dosage should not exceed 100 mg. If doses greater than 50 mg are deemed necessary, the next dose and succeeding doses should be increased cautiously in increments of 12.5 mg.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.