|Trade names||Compazine, others|
|By mouth, rectal, IM, IV|
|Bioavailability||Unknown, but presumed substantial|
|Metabolism||Mainly hepatic (CYP2D6 and/or CYP3A4)|
|Elimination half-life||4–8 hours, differs with the method of administration|
|Excretion||Biliary, (colored) inactive metabolites in urine|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||373.943 g/mol g·mol−1|
|3D model (JSmol)|
Prochlorperazine, sold under the brand name Compazine among others, is a medication used to treat nausea, schizophrenia, migraines, and anxiety. It is a less preferred medication for anxiety. It may be taken by mouth, rectally, injection into a vein, or injection into a muscle.
Common side effects include sleepiness, blurry vision, low blood pressure, and dizziness. Serious side effects may include movement disorders including tardive dyskinesia and neuroleptic malignant syndrome. Use in pregnancy and breastfeeding is generally not recommended. It is a typical antipsychotic which is believed to work by affecting levels of dopamine in the brain.
Prochlorperazine was approved for medical use in the United States in 1956. It is available as a generic medication. A dose in the United Kingdom costs the NHS about £0.04 as of 2019. In the United States the wholesale cost of this amount is about US$0.24. In 2016 it was the 288th most prescribed medication in the United States with more than a million prescriptions.
Prochlorperazine is used to prevent vomiting caused by chemotherapy, radiation therapy and in the pre- and postoperative setting. A 2015 Cochrane review found no differences in efficacy among drugs commonly used for this purpose in emergency rooms.
In the UK, prochlorperazine is available for the treatment of nausea caused by migraine as a tablet dissolved in the mouth; it is sold as a "pharmacy medicine", meaning it does not require a prescription but is only available after talking with a pharmacist.
Sedation is very common, and extrapyramidal side effects are common and include restlessness, dystonic reactions, pseudoparkinsonism, and akathisia; the extrapyramidal symptoms can affect 2% of people at low doses, whereas higher doses may affect as many as 40% of people.
Prochlorperazine can also cause a life-threatening condition called neuroleptic malignant syndrome (NMS). Some symptoms of NMS include high fever, stiff muscles, neck muscle spasm, confusion, irregular pulse or blood pressure, fast heart rate (tachycardia), sweating, abnormal heart rhythms (arrhythmias). Research from the Veterans Administration and United States Food and Drug Administration show injection site reactions. Adverse effects are similar in children.
The British National Formulary recommends a gradual withdrawal when discontinuing antipsychotics to avoid acute withdrawal syndrome or rapid relapse. Symptoms of withdrawal commonly include nausea, vomiting, and loss of appetite. Other symptoms may include restlessness, increased sweating, and trouble sleeping. Less commonly there may be a feeling of the world spinning, numbness, or muscle pains. Symptoms generally resolve after a short period of time.
There is tentative evidence that discontinuation of antipsychotics can result in psychosis. It may also result in reoccurrence of the condition that is being treated. Rarely tardive dyskinesia can occur when the medication is stopped.
Prochlorperazine is analogous to chlorpromazine; both of these agents antagonize dopaminergic D2 receptors in various pathways of the central nervous system. This D2 blockade results in antipsychotic, antiemetic and other effects. Hyperprolactinemia is a side effect of dopamine antagonists as blockade of D2 receptors within the tuberoinfundibular pathway results in increased plasma levels of prolactin due to increased secretion by lactotrophs in the anterior pituitary.
Following intramuscular injection, the antiemetic action is evident within 5 to 10 minutes and lasts for 3 to 4 hours. Rapid action is also noted after buccal treatment. With oral dosing, the start of action is delayed but the duration somewhat longer (approximately 6 hours).
Prochlorperazine is available as tablets, suppositories, and in an injectable form.
As of September 2017 it was marketed under the trade names Ametil, Antinaus, Buccastem, Bukatel, Chlormeprazine, Chloropernazine, Compazine, Compro, Daolin, Dhaperazine, Emedrotec, Emetiral, Eminorm, Lotamin, Mitil, Mormal, Nautisol, Novamin, Novomit, Proazine, Procalm, Prochlorperazin, Prochlorperazine, Prochlorpérazine, Prochlorperazinum, Prochlozine, Proclorperazina, Promat, Promin, Promtil, Roumin, Scripto-metic, Seratil, Stemetil, Steremal, Vergon, Vestil, and Volimin.
Alexza Pharmaceuticals studied an inhaled form of prochlorperazine for the treatment of migraine through Phase II trials under the development name AT-001; development was discontinued in 2011.
Withdrawal of antipsychotic drugs after long-term therapy should always be gradual and closely monitored to avoid the risk of acute withdrawal syndromes or rapid relapse.