What should clinicians know about fluphenazine decanoate (“Prolixin Dec”)?

Fluphenazine Decanoate
Indication(s)	Schizophrenia
Dosing available as prefilled syringes	Prolixin Dec is directly drawn up from a 5 ml vial with a 25 mg/ml concentration that can be stored after each use and used until empty.
Recommended starting and maintenance dose	In patients new to Prolixin Dec, dose titration can be used but is not required. Initiate with 6.25 mg IM/SC, followed dose adjustments in between 6.25 to 12.5 mg increments every two weeks until the target dose is reached. If using dose titration, overlap with oral fluphenazine for one to two months while building up Prolixin Dec. Most patients will be well maintained on a Prolixin Dec dose of 6.25 to 25 mg IM/SC every two weeks (covering the dose range of 5 to 20 mg oral fluphenazine daily); only a minority of patients should need high-dose regimens of 37.5 or 50 mg IM/SC every two weeks. Therapeutic drug monitoring (TDM) can guide dosing. A fluphenazine plasma level between 1 and 10 is a therapeutic target range.
Drug Metabolizing Enzyme	CYP2D6
Loading dose	Not established
Oral overlap	There is no exact conversion for oral to long-acting IM/SC. 10 mg fluphenazine daily corresponds to Prolixin Dec 12.5 IM/SC every three weeks. The highest individual dose is listed in the package insert as 100 mg IM (but see below). Patient response should always be the indicator of appropriate dosing.
Establishing tolerability	Prior to initiating Prolixin Dec, establish tolerability with oral fluphenazine in fluphenazine-naïve patients.
Storage	Room temperature
Reconstitution or mixing	N/A
Injection site	Deltoid or gluteal injections are both possible; the site can be chosen based on patient preference and body habitus. Alternate sites and use 1-inch needle for deltoid, 2-inch needle for gluteal injection. Give by deep intramuscular injection and use the Z-track technique to avoid leakage.
Injection interval	Prolixin Dec is typically given IM every two weeks; there is, however, flexibility around the injection interval and injections up to every 6 weeks have been used.
Preparation	As this is a sesame oil vehicle, it may be pulled out of vial with a larger gauge needle (i.e. 18 gauge) then injected with a new, smaller gauge needle (i.e. 21 gauge) for patient comfort
Administration considerations	Prolixin Dec is oil-based (sesame oil) which is more painful than water-based long-acting injectables. You also will need to push harder. Avoid giving more than 3 cc as a single injection. Therapeutic drug monitoring (TDM) can guide dosing. A fluphenazine plasma level between 1 and 10 is a therapeutic target range.
When a dose is missed	For those patients who are scheduled to receive Prolixin Decanoate injections every 4 weeks and who have received at least two previous injections as scheduled, the next dose should be administered not later than 8 weeks after the last injection. For those patients who are scheduled to receive Prolixin Decanoate injections every 2 or 3 weeks, medical staff should be consulted for any missed doses. For more information review this tip.
REMS	No
Additional information	Sesame oil base - check for sesame allergy.

Dose Conversion of Oral Fluphenazine to Fluphenazine Decanoate LAI
PO Dose - Fluphenazine	LAI/IM Dose - Fluphenazine Decanoate
Initial LAI dose	Suggested 6.25 mg every 2 weeks (or calculated at 1.25 mg x PO dose every 3-6 weeks)
10 mg daily	12.5 mg (0.5 ml) every 3 weeks [can be given every 2 weeks]
20 mg daily	25 mg (1 ml) every 3 weeks
30 mg daily	37.5 mg (1.5 ml) every 3-6 weeks
40 mg daily	50 mg (2 ml) every 3-6 weeks
Typical dose: 6.25-25 mg every 2-4 weeks. General conversion formula: For each 10 mg/day PO, give 12.5 mg decanoate every 3 weeks. Increase by 12.5 mg increments if doses >50 mg needed. Recommended available dose formulations include 25mg/ml strength, in 5ml multiple does vials. Dose reduction may be necessary for CYP450 interactions of side effect intolerance. References: 1. APP Pharmaceuticals. (2010). Fluphenazine decanoate, injection usp. 2. American Psychiatric Association. (2020). The American Psychiatric Association Practice Guideline for the Treatment of Patients With Schizophrenia. American Psychiatric Association Publishing. https://doi.org/10.1176/appi.books.9780890424841

Practical issues (including administration)

Prolixin Dec does not need to be refrigerated or reconstituted. Prolixin Dec is directly drawn up from a 5 ml vial with a 25 mg/ml concentration that can be stored after each use and used until empty.
Deltoid or gluteal injections are both possible; the site can be chosen based on patient preference and body habitus. Alternate sites and use 1-inch needle for deltoid, 2-inch needle for gluteal injection. The package labeling also includes a subcutaneous injection site option, but injection volume may limit this injection type.
Give by deep intramuscular injection and use the Z-track technique to avoid leakage.
Prolixin Dec is oil-based (sesame oil) which is more painful than water-based long-acting injectables. You also will need to push harder. Avoid giving more than 3 cc as a single injection.

FDA Medication Label

Information on this topic is found in the FDA medication label. Not all information in the FDA medication label is included here, and clinicians should read the entire FDA medication label before making treatment decisions.

Prescribing should always be informed by the FDA medication label. Medication labels can be found by searching Drugs@FDA at the FDA website. Labels are also available using the Drugs@FDA app for Apple or Android devices.

Labels change over time, and the current label should always be consulted. Here is the most recent label, at time of writing.

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