Fluphenazine Decanoate

Danielle J Harrison
Author: Danielle J Harrison Medical Reviewer: Tayler Hackett Last updated:

Fluphenazine Decanoate is a typical, first-generation antipsychotic drug, of the phenothiazine class, used to treat schizophrenia. You should always consult with your doctor if you are taking any other medications, have allergies, or have been diagnosed with other medical conditions, as misuse of Fluphenazine can have dangerous consequences.

Fluphenazine decanoate brand names

Fluphenazine decanoate is commonly sold under the following brand names:

  • Prolixin (discontinued)
  • Permitil
  • Modecate

What is fluphenazine decanoate prescribed for?

Fluphenazine decanoate is primarily used to treat patients with schizophrenia.It is delivered through a long-acting injection, and used for maintenance therapy. For most patients, fluphenazine decanoate can control schizophrenic symptoms 4 week or longer. [3]

How does fluphenazine decanoate work?

Fluphenazine decanoate blocks dopamine receptors in the brain. It is believed that this mechanism helps to treat symptoms of psychosis, such as hallucinations and delusions, that are related to a chemical imbalance with the dopamine neurotransmitter. [1]

How is fluphenazine decanoate usually taken?

Fluphenazine decanoate is administered by a healthcare provider through an intramuscular injection (in the muscle) or subcutaneous injection (underneath the skin). [3] The gluteal muscle is the most common injection site. Doses range from 12.5mg to 100mg every two to five weeks. [1] The usual starting dose is between 12.5mg and 25mg. [3] The most common frequency is every four weeks. [1]

Fluphenazine decanoate is sometimes prescribed after you have been on a stable dose of the oral form of fluphenazine for a period of time, in order to minimize the risk of serious adverse reactions. [3]

Your doctor will carefully monitor your symptoms and adjust your dose as needed. They will also monitor for potentially serious adverse effects, as they can be unpredictable. If you miss an appointment for a scheduled dose, make a new one as soon as possible.

How long does fluphenazine decanoate stay in your system?

Fluphenazine decanoate usually begins to work within the body between 24 and 72 hours after injection, but it usually takes 48 to 96 hours for effects to become noticeable. [3] Effects of fluphenazine decanoate last around four weeks on average. [1]

The half-life of fluphenazine decanoate is 6.8 to 9.6 days. [1] This increases to 14.3 days after multiple injections. [4] Half-life is the time it takes for the medication in your system to decrease by half. It is still detectable in plasma up to six months after the last injection. [2]

Fluphenazine decanoate side effects

Fluphenazine decanoate can cause adverse reactions in some people. Listed below are some of the most common side effects.

Mild side effects

  • Pain at injection site
  • Dizziness or lightheadedness
  • Headache
  • Nausea
  • Sweating
  • Constipation
  • Dry mouth
  • Loss of appetite
  • Blurred vision
  • Bizarre dreams [8]

Severe side effects

  • Feelings of restlessness (tardive akathisia)
  • A ‘mask-like’ or blank facial expression
  • Tremors
  • Foot or ankle swelling
  • Fainting
  • Skin discoloration
  • Seizures
  • Joint pain
  • Difficulty urinating/frequent urination
  • Butterfly-shaped rash on the face
  • Decreased sexual ability
  • Irregular menstrual periods
  • Erection lasting more than four hours
  • Yellowing of the skin or eyes
  • Severe abdominal pain
  • Easy bleeding or bruising
  • Weight changes
  • Signs of infection (for instance, a fever or sore throat that wont go away)
  • Rapid heartbeat [3][8]

Tardive dyskinesia

Tardive dyskinesia is a relatively rare condition that can occur with continued use of antipsychotic drugs. It can cause repetitive, involuntary movements, especially in the mouth, face, neck, arms, and legs. Consult with your doctor if you notice the following signs:

  • Lip smacking and uncontrollable tongue movements
  • Grimacing
  • Difficulty swallowing
  • Neck twisting
  • Jerky leg and arm movements [3]

Neuroleptic malignant syndrome

Neuroleptic Malignant Syndrome is a rare but potentially fatal condition that can occur when taking antipsychotics. Seek immediate medical attention if you experience the following symptoms:

  • High fever
  • Irregular or racing heartbeat
  • High or low blood pressure
  • Confusion
  • Fainting or loss of consciousness
  • Muscle stiffness
  • Sweating [3]

Increased prolactin levels

Rarely, fluphenazine decanoate can lead to high prolactin levels. Too much of this hormone can decrease the production of estrogen and testosterone, which can cause:

  • Irregular or absent menstrual periods
  • Sexual dysfunction
  • Enlarged breasts in men
  • Unusual breast milk (in men and women)
  • Fertility problems [8]

If you experience mild side effects that are bothersome or do not subside, contact your doctor to discuss your options. If you notice any severe side effects, seek immediate medical care from your doctor or the nearest emergency room.

Fluphenazine decanoate precautions

Before taking this medication, tell your healthcare provider if you are pregnant or breastfeeding. Tell them about any allergies, especially to other phenothiazines, such as chlorpromazine or perphenazine, as fluphenazine can cause severe allergic reactions. [3] Inform your doctor of any other medications you are taking, and if you have a history of any medical conditions, including:

  • Glaucoma
  • An enlarged prostate
  • Seizures
  • An overactive thyroid
  • Liver disease
  • Kidney disease
  • Heart disease
  • Pregnant, plan to become pregnant, or are breastfeeding
  • Dementia [9]

When you first start taking this medication, avoid driving or operating heavy machinery until you know how it affects you. Avoid getting up too fast, as you may experience dizziness or a drop in blood pressure.

While taking this medication, you should avoid alcohol, tobacco, and marijuana. [7] You should avoid extreme heat, as fluphenazine decanoate can increase the risk of heat stroke. [7] Use sunscreen and limit your time in the sun, as this medication can also increase sun sensitivity. [7]

Fluphenazine decanoate interactions

The following medications are known to have potentially dangerous interactions with fluphenazine decanoate. Please note that this list is not exhaustive and only lists the most severe drug interactions. Always inform your doctor of all other medications you are taking.

  • Lithium
  • Guanethidine and guanadrel
  • Any dopamine agonists such as levodopa, cabergoline and pergolide
  • Atropine or other anticholinergics
  • Any medication that causes drowsiness (such as opioids, muscle relaxants, antihistamines, and others) [7]

Fluphenazine decanoate storage

While taking fluphenazine decanoate, your pharmacy or healthcare provider will store the drug between injection appointments. It will be stored at room temperature, away from moisture or light. [7] Your healthcare provider will check for any debris or changes in color of the liquid before administering. [7]

What to do if you overdose on fluphenazine decanoate

Overdoses of fluphenazine decanoate are uncommon, as the medication is administered by a healthcare provider. However, if it does occur, symptoms could include:

  • Shallow breathing
  • Fast or irregular heartbeat
  • Seizures
  • Loss of consciousness

Although rare, there have been cases of death from overdose [6], so it’s important to seek immediate help from your physician or at your nearest emergency room. Following an overdose, your doctor will stop all injections until you show signs of relapse. Then, the dosage will be decreased. [6]

Is flupenthixol the same as fluphenazine?

Flupenthixol and fluphenazine are two different typical antipsychotic drugs with similar properties. They both have similar effects on psychotic symptoms, but fluphenazine is stronger. A 25mg dose of fluphenazine decanoate is roughly equivalent to a 40mg dose of flupenthixol decanoate. [5]

  1. Abbas, F., Rajab, T., Alsamarrai, O., Alhalabi, N., Zaher Addeen, S., Mheish, O., Aljojo, A., & Essali, A. (2017). Fluphenazine decanoate (timing of administration) for people with schizophrenia. The Cochrane Database of Systematic Reviews, 2017(10), CD012810. https://doi.org/10.1002/14651858.CD012810
  2. Carpenter, W.T., Buchanan, R.W., Kirkpatrick, B., Lann, H.D., Breier, A.F., & Summerfelt, A.T. (1999). Comparative Effectiveness of Fluphenazine Decanoate Injections Every 2 Weeks Versus Every 6 Weeks. The American Journal of Psychiatry, 156 (3), 412-418. https://doi.org/10.1176/ajp.156.3.412
  3. DailyMed. (2019). Fluphenazine decanoate. National Institutes of Health. Retrieved October 20, 2022, from https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f8ba014e-aea0-49bc-8345-4e0a384b484e
  4. Jann, M. W., Ereshefsky, L., & Saklad, S. R. (1985). Clinical pharmacokinetics of the depot antipsychotics. Clinical pharmacokinetics, 10(4), 315–333. https://doi.org/10.2165/00003088-198510040-00003
  5. Johnson, D. A., & Malik, N. A. (1975). A double-blind comparison of fluphenazine decanoate and flupenthixol decanoate in the treatment of acute schizophrenia. Acta psychiatrica Scandinavica, 51(4), 257–267. https://doi.org/10.1111/j.1600-0447.1975.tb11092.x
  6. Staff, H. (2009, January 4). Fluphenazine Decanoate Full Prescribing Information. HealthyPlace. Retrieved on 2022, October 20 from https://www.healthyplace.com/other-info/psychiatric-medications/fluphenazine-decanoate-prolixin-permitil-modecate-full-prescribing-information
  7. Fluphenazine Uses, Side Effects & Warnings. (n.d.). Drugs.com. https://www.drugs.com/mtm/fluphenazine.html
  8. Fluphenazine Decanoate – Injection | HealthLink BC. (n.d.). https://www.healthlinkbc.ca/medications/fluphenazine-decanoate-injection
  9. Fluphenazine: MedlinePlus Drug Information. (n.d.). https://medlineplus.gov/druginfo/meds/a682172.html
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Danielle J Harrison
Author Danielle J Harrison Writer

Danielle J. Harrison is writer and mental health counselor with a master's degree from The City College of New York.

Published: Nov 22nd 2022, Last edited: Feb 21st 2024

Tayler Hackett
Medical Reviewer Tayler Hackett BSc, PGCert

Talyer Hackett is a medical writer and researcher with 10+ years of experience, holding B.A. in Psychology from the University of Liverpool.

Content reviewed by a medical professional. Last reviewed: Nov 23rd 2022