What is the typical dosing regimen for Prolixin (fluphenazine) decanoate?

Prolixin (Fluphenazine) Decanoate Dosing Regimen

The typical dosing regimen for Prolixin (fluphenazine) decanoate is 12.5 to 25 mg (0.5 to 1 mL) intramuscularly or subcutaneously for initial therapy, with subsequent injections and dosage intervals determined according to the patient's response. 1

Initial Dosing Approach

• For most patients, begin with 12.5 to 25 mg (0.5 to 1 mL) intramuscularly or subcutaneously to initiate therapy 1
• Onset of action generally appears between 24 and 72 hours after injection, with significant effects on psychotic symptoms within 48 to 96 hours 1
• A dry syringe and needle of at least 21 gauge should be used (wet needle or syringe may cause solution cloudiness) 1

Dosing Conversion from Oral Fluphenazine

• For patients stabilized on oral fluphenazine, an approximate conversion ratio is 12.5 mg (0.5 mL) of decanoate every three weeks for every 10 mg of fluphenazine hydrochloride taken daily 1
• A controlled study showed that 20 mg fluphenazine hydrochloride daily was equivalent to 25 mg (1 mL) of fluphenazine decanoate injection every three weeks 1
• After conversion to fluphenazine decanoate, careful clinical monitoring and appropriate dosage adjustment should be made at each injection 1

Maintenance Dosing

• When administered as maintenance therapy, a single injection may control schizophrenic symptoms for up to four weeks or longer 1
• In some patients on maintenance therapy, response to a single dose has lasted as long as six weeks 1
• Dosage should not exceed 100 mg 1
• If doses greater than 50 mg are necessary, increase cautiously in increments of 12.5 mg 1

Special Patient Considerations

• For "poor risk" patients (those with known hypersensitivity to phenothiazines or with predisposing disorders), therapy should be initiated cautiously with oral or parenteral fluphenazine hydrochloride before converting to the decanoate form 1
• For severely agitated patients, consider initial treatment with a rapid-acting phenothiazine compound before administering 25 mg (1 mL) of fluphenazine decanoate 1
• Patients with no history of taking phenothiazines should be treated initially with a shorter-acting form of fluphenazine before administering the decanoate to determine response and establish appropriate dosage 1

Monitoring and Adverse Effects

• Fluphenazine decanoate is associated with significant side effects involving the cholinergic, cardiovascular, and extrapyramidal systems 2
• There is an inherent risk of irreversible tardive dyskinesia, which can develop in 50% of elderly patients after continuous use of typical antipsychotic agents for 2 years 2
• If extrapyramidal symptoms occur, decrease dosage or switch to another agent; avoid use of benztropine or trihexyphenidyl 2
• Research has not found a relationship between plasma levels of fluphenazine and clinical outcomes or side effects, suggesting limited utility of therapeutic drug monitoring 3

Clinical Considerations

• Fluphenazine decanoate is considered a second-line therapy for patients who cannot tolerate or do not respond to atypical antipsychotic agents 2
• In clinical trials, fluphenazine decanoate has shown similar efficacy to other depot antipsychotics but with fewer extrapyramidal side effects compared to oral neuroleptics 4
• Substance use among patients receiving fluphenazine decanoate is a major predictor of relapse and should be carefully monitored 5

Fluphenazine decanoate requires individualized dosing with careful monitoring for optimal efficacy and minimal side effects. The optimal amount and frequency of administration must be determined for each patient, as dosage requirements vary with clinical circumstances and individual response 1.