How do you take Fluphenazine decanoate?

This is not a drug you take at home; it is given as an injection by a doctor or nurse, usually into your buttock or upper arm muscle. The usual starting dose for adults is 12.5 mg to 25 mg, and it is given once every 2 to 4 weeks. Your doctor will adjust the dose based on how you respond. You must keep all your injection appointments so the medicine keeps working.

What are the side effects of Fluphenazine decanoate?

Feeling sleepy or drowsy, dry mouth, stiffness or tightness in the muscles, restlessness or inability to sit still, mild dizziness especially when standing up quickly

Who should not take Fluphenazine decanoate?

People who are allergic to fluphenazine or similar medicines (phenothiazines), people with severe liver damage, people with blood disorders, people in a coma or deeply sedated state, people with brain damage, and people with a condition called pheochromocytoma (a rare tumor). Elderly patients with dementia should also avoid it.

Prescription

Antipsychotic (long-acting)

Fluphenazine decanoate

Last reviewed July 2026

Who is this for?

For adults (18+). Standard adult dosing applies: see the How to Take tab for full instructions.

What is this drug?

Fluphenazine decanoate is a long-acting injection used to calm the brain and control symptoms of serious mental illness. It works by blocking certain chemicals in the brain (especially dopamine) that cause confused thinking, hearing voices, or unusual behavior.

How it works

Blocks dopamine D2 receptors in the mesolimbic and mesocortical pathways of the brain, reducing psychotic symptoms; the decanoate ester formulation provides sustained release over 3-4 weeks, ensuring prolonged antipsychotic effect and improved treatment adherence.

What is it used for?

Schizophrenia (mental illness with hearing voices, confused thinking, seeing things that are not there), other serious mental health conditions that need long-term treatment

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Depression & Mental Health Schizophrenia & Psychosis

Prescription Required

You need a doctor's prescription to buy this drug.

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What to watch out for

Only get this injection from a licensed hospital, clinic, or pharmacy; never buy from roadside sellers or unregistered sources, as fake or expired injections are dangerous. Do not stop your injection schedule without your doctor's approval, even if you feel better, as stopping suddenly can make your mental health condition return or worsen. If you notice any unusual body movements or shaking, report to your doctor immediately.

Common Side Effects

Feeling sleepy or drowsy
dry mouth
stiffness or tightness in the muscles
restlessness or inability to sit still
mild dizziness especially when standing up quickly

Serious Side Effects

Uncontrollable movements of the face
tongue
or body (this can become permanent if not reported early)
high fever with stiff muscles and confusion (this is a medical emergency called neuroleptic malignant syndrome)
and severe difficulty breathing or swallowing. Go to the hospital immediately if any of these happen.

Drug Interactions

Avoid drinking alcohol while on this medication as it can make drowsiness and dizziness much worse. Be careful with other medicines that make you sleepy such as antihistamines (like chlorpheniramine or promethazine) or sedatives. Tell your doctor if you are taking blood pressure medicine, as fluphenazine can cause your blood pressure to drop too low.

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Pregnancy & Breastfeeding Warning

This drug is not considered safe during pregnancy or breastfeeding. Consult your doctor immediately if you are pregnant, planning to become pregnant, or breastfeeding.

Who Should NOT Take This

People who are allergic to fluphenazine or similar medicines (phenothiazines)
people with severe liver damage
people with blood disorders
people in a coma or deeply sedated state
people with brain damage
and people with a condition called pheochromocytoma (a rare tumor). Elderly patients with dementia should also avoid it.

How to Store

Store in a cool, dry place away from direct sunlight and heat. Nigerian weather can be very hot, so do not leave it near windows or in cars. Keep it at room temperature or in a refrigerator if possible. Always keep away from children. This injection is usually stored and handled at the hospital or clinic.

For information only: not medical advice. Always talk to a doctor or pharmacist before changing your medication.