Bedside Snapshot
  • Core Use: Phenothiazine antipsychotic used at lower doses primarily as a potent antiemetic and migraine adjunct; at higher doses has antipsychotic effects
  • Onset/Duration: IV/IM onset 5–20 minutes; oral/rectal onset 30–60 minutes; duration ~6–12 hours
  • Key Danger: Acute dystonic reactions, akathisia, sedation, orthostatic hypotension, QT prolongation, and rare neuroleptic malignant syndrome (NMS)
  • Special Note: Often paired with diphenhydramine 25–50 mg IV/IM to reduce risk of extrapyramidal symptoms; use caution in elderly and those with cardiac disease
Contraindications

Absolute Contraindications:

  • Known hypersensitivity to prochlorperazine or other phenothiazines
  • Comatose states or severe CNS depression from any cause (e.g., concurrent high-dose CNS depressants)
  • Children under 2 years of age or <9 kg
  • Severe hypotension or circulatory collapse (relative/strong caution)

Major Precautions:

  • Elderly patients with dementia-related psychosis have an increased risk of death with antipsychotic drugs (class boxed warning); minimize dose and duration
  • Use cautiously in patients with QT prolongation, electrolyte abnormalities, or those on other QT-prolonging drugs (e.g., certain antiarrhythmics, macrolides, fluoroquinolones)
  • May lower seizure threshold; caution in patients with seizure disorders or on other pro-convulsant medications
  • Orthostatic hypotension and sedation are common; monitor hemodynamics in volume-depleted or critically ill patients
  • History of extrapyramidal symptoms (EPS) or parkinsonism: prochlorperazine can worsen motor symptoms; consider alternatives
  • Pregnancy: generally avoided in the first trimester unless benefits clearly outweigh risks; short-term use for refractory hyperemesis may be considered under obstetric guidance
⚠️ Boxed Warning: Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at increased risk of death. Prochlorperazine is not approved for dementia-related psychosis.
Adverse Effects

Common:

  • Sedation, dizziness, fatigue
  • Orthostatic hypotension, mild tachycardia
  • Dry mouth, constipation, blurred vision (anticholinergic effects)
  • Injection-site pain (IM) or irritation (IV)

Serious:

  • Extrapyramidal symptoms (EPS): acute dystonia (torticollis, oculogyric crisis), akathisia, parkinsonism
  • Neuroleptic malignant syndrome (NMS): hyperthermia, rigidity, autonomic instability, altered mental status
  • Tardive dyskinesia with chronic use, especially in elderly women
  • QT prolongation and torsades de pointes, particularly with other risk factors (hypokalemia, hypomagnesemia, other QT-prolonging medications)
  • Severe hypotension, syncope, or arrhythmias, especially with IV dosing
  • Hematologic effects (rare): leukopenia, agranulocytosis; monitor for signs of infection with prolonged therapy
Monitoring

Clinical Monitoring:

  • Clinical response: resolution of nausea/vomiting or migraine symptoms; reassess for alternative diagnosis if no benefit
  • Mental status, level of sedation, and ability to protect airway, especially in combination with opioids or other sedatives
  • Blood pressure and heart rate (watch for orthostatic hypotension and tachycardia)
  • Neurologic exam for early signs of EPS (restlessness, neck stiffness, oculogyric crisis, tongue protrusion)

Laboratory/Diagnostic Monitoring:

  • ECG monitoring in high-risk patients (known QT prolongation, on other QT-prolonging drugs, or significant electrolyte disturbances)
  • Electrolytes (potassium, magnesium) in patients at risk for QT prolongation
Drug Names & Classification

Generic Name: Prochlorperazine

Brand Names: Compazine, Compro (generic available)

Drug Class: Phenothiazine derivative; dopamine (D₂) receptor antagonist; antipsychotic and antiemetic

Mechanism of Action
  • Blocks dopamine D₂ receptors in the chemoreceptor trigger zone (CTZ) of the medulla, reducing stimulation of the vomiting center and thereby decreasing nausea and vomiting
  • At higher or repeated doses, antagonism of D₂ receptors in mesolimbic pathways contributes to antipsychotic effects
  • Exhibits alpha-adrenergic, anticholinergic (muscarinic), and antihistaminic activity, contributing to sedation, orthostatic hypotension, and some of its side-effect profile
  • Like other phenothiazines, can affect cardiac repolarization (QT prolongation) and lower seizure threshold
Pharmacokinetics
  • Absorption: Oral and rectal formulations are well absorbed; onset of antiemetic effect within 30–60 minutes by mouth or rectal; IV/IM onset typically within 5–20 minutes
  • Distribution: Highly protein bound; widely distributed, including CNS; relatively large volume of distribution consistent with lipophilicity
  • Metabolism: Primarily hepatic via oxidative pathways; subject to first-pass metabolism with oral administration
  • Elimination: Metabolites excreted in urine and feces; terminal half-life roughly 6–12 hours, allowing q6h dosing for antiemetic use
  • Special Populations: Hepatic impairment can increase exposure; use lower doses and monitor for adverse CNS effects in liver disease and the elderly
Common ED/ICU Indications
  • Symptomatic treatment of nausea and vomiting due to a variety of causes (e.g., migraine, gastroenteritis, medication-related) once emergent etiologies are addressed
  • Adjunct treatment of acute migraine in the ED, often combined with diphenhydramine and IV fluids with or without NSAIDs
  • Short-term control of severe nausea and vomiting associated with chemotherapy (historically; now often secondary to newer antiemetics)
  • Antipsychotic use (e.g., schizophrenia) is less common in ED/ICU where other agents (e.g., haloperidol) are usually preferred
Available Forms & Strengths
  • Injection (IV/IM): Commonly 5 mg/mL in 2 mL vials (10 mg total per vial; may vary by product)
  • Tablets: 5 mg, 10 mg immediate-release tablets
  • Rectal Suppositories: 25 mg (often dosed every 12 hours)
  • Oral Liquid: Formulations exist in some markets; verify concentration prior to dosing
Dosing – Prochlorperazine (Adult Antiemetic/Migraine)

Always follow local guidelines and institutional protocols.

Route / Scenario Typical Dose Frequency Notes
IV Antiemetic / Migraine 10 mg IV Once; may repeat every 4–6 hours as needed Give slowly over 2–5 minutes; often pair with 25–50 mg diphenhydramine IV
IM Antiemetic / Migraine 10 mg IM Once; may repeat every 3–4 hours as needed Onset slower than IV; monitor for sedation, hypotension
PO Antiemetic (short-term) 5–10 mg PO Every 6–8 hours as needed Max typical total about 40 mg/day; use lowest effective dose
Rectal Suppository 25 mg PR Every 12 hours as needed Useful when vomiting prevents PO use and IV access is not available
Elderly or Frail 2.5–5 mg IV/IM/PO Every 6–8 hours as needed Higher risk of EPS, sedation, orthostatic hypotension; titrate cautiously
Maximum Daily Dose 30–40 mg/day Divided doses Higher doses approach antipsychotic ranges and increase side effects
Antipsychotic Dosing 5–10 mg PO/IM Every 6–8 hours; titrate per psychiatry ED/ICU use is uncommon; usually other agents preferred

Pediatric Use (outline):

  • Avoid use in children under 2 years of age or <9 kg due to increased risk of extrapyramidal reactions and respiratory depression
  • In older children, use is restricted and alternative antiemetics (e.g., ondansetron) are often preferred for routine nausea and vomiting
  • If used, dosing is weight-based with tight age/weight restrictions and maximums; follow institutional pediatric guidelines strictly
Clinical Pearls
💡 Co-administration with Diphenhydramine: In the ED, prochlorperazine 10 mg IV/IM is often paired with diphenhydramine 25–50 mg IV/IM to reduce the risk of acute dystonic reactions and akathisia.
⚠️ Acute Dystonia Treatment: If acute dystonia occurs (e.g., neck spasm, oculogyric crisis), treat promptly with diphenhydramine or benztropine and avoid further phenothiazine use.
ℹ️ Ondansetron vs. Prochlorperazine: Ondansetron is often preferred for routine nausea due to a more favorable side-effect profile, but prochlorperazine can be very helpful in migraine-associated nausea or when ondansetron fails.
⚠️ Special Caution in Older Adults: Elderly patients are much more prone to EPS, orthostatic hypotension, and sedation; start low and go slow. Consider alternative antiemetics when possible.
💡 QT Prolongation Risk: Check for other QT-prolonging medications and correct electrolytes (potassium, magnesium) before and during therapy in high-risk cardiac patients.
ℹ️ IV Administration: Always administer IV prochlorperazine slowly over 2–5 minutes to minimize risk of hypotension and other adverse effects.
References
  1. Lexicomp. (2024). Prochlorperazine: Drug information. Wolters Kluwer.
  2. Tintinalli, J. E., Ma, O. J., & Yealy, D. M. (2016). Tintinalli's emergency medicine: A comprehensive study guide (8th ed.). McGraw-Hill Education.
  3. American Headache Society. (2016). Management of adults with acute migraine in the emergency department. Headache, 56(6), 911–940. https://doi.org/10.1111/head.12864
  4. U.S. Food and Drug Administration. (2024). Compazine (prochlorperazine) prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/011717s043lbl.pdf
  5. Friedman, B. W., Esses, D., Solorzano, C., Choi, H. K., Cole, M., Davitt, M., Bijur, P. E., & Gallagher, E. J. (2008). A randomized controlled trial of prochlorperazine versus metoclopramide for treatment of acute migraine. Annals of Emergency Medicine, 52(4), 399–406. https://doi.org/10.1016/j.annemergmed.2008.01.333
Back to Medication Index
Medical Disclaimer
  • For Educational Purposes Only: This content is intended for educational reference and should not be used for clinical decision-making.
  • Not a Substitute for Professional Judgment: Always consult your local protocols, institutional guidelines, and supervising physicians.
  • Verify Before Acting: Users are responsible for verifying information through authoritative sources before any clinical application.
AI Assistance Notice
AI was used to assist in organizing and formatting this information. All content is reviewed for accuracy.