Pharmacology · Dopamine-antagonist antiemetics and prokinetics
Prochlorperazine !
A phenothiazine that blocks dopamine in the vomiting centre. It controls severe nausea but can cause dystonia, low blood pressure and sedation.
Updated 2026-11-01
No structure of prochlorperazine bound to D2 exists; the figure shows haloperidol, another antipsychotic, in the same dopamine pocket of the human D2 receptor.
Mechanism of action
Prochlorperazine is a piperazine phenothiazine. Like the other phenothiazines it blocks dopamine D2 receptors in the chemoreceptor trigger zone, which depresses the vomiting reflex, and it also has an antipsychotic effect. It blocks α-adrenergic receptors and has anticholinergic effects, which explain low blood pressure, blurred vision and dry mouth.
- Blocks D2 receptors in the chemoreceptor trigger zone
- The vomiting reflex is depressed: less nausea
- α1 block and anticholinergic effects add hypotension and dry mouth
- D2 block in the basal ganglia causes dystonia and akathisia
Pharmacokinetics
- Absorption
- Given by mouth (tablets), rectally (suppositories), intramuscularly or intravenously.
- Onset and duration
- After an intramuscular dose it acts within 10–20 minutes and lasts about 3–4 hours.
Indications
- Control of severe nausea and vomiting.
- Schizophrenia. Schizophrenia →
Adverse effects
Common
- Drowsiness and dizziness
- Low blood pressure, especially after injection
- Blurred vision and dry mouth
- Amenorrhoea and skin reactions
Contraindications
- Hypersensitivity to phenothiazines
- Coma or large amounts of CNS depressants (alcohol, barbiturates, opioids)
- Children under 2 years or under the weight set in the label
- Bone marrow depression or a prior blood dyscrasia or jaundice from a phenothiazine (unless benefit clearly outweighs risk)
Key interactions
- Alcohol, anaesthetics, opioids and other CNS depressants
- Deeper and longer sedation.
- Epinephrine
- Phenothiazines block α receptors, so epinephrine can lower blood pressure further; norepinephrine or phenylephrine are used if a vasopressor is needed.
- Thiazide diuretics and antihypertensives
- More orthostatic hypotension.
- Propranolol
- Higher levels of both drugs.
- Anticonvulsants and phenytoin
- Lower seizure threshold, and phenytoin toxicity reported.
- Lithium
- Rare encephalopathic syndrome with antipsychotics.
What is monitored
- Blood pressure lying and standing, especially after injection
- Abnormal movements (dystonia, akathisia, tardive dyskinesia)
- Complete blood count in patients with low white cells or prior drug-induced neutropenia
- Temperature and muscle rigidity (neuroleptic malignant syndrome)
Administration and safety
- Not given subcutaneously, because it irritates the tissue
- After an injection the patient stays lying down and is observed for at least half an hour because of hypotension
- Staff avoid skin contact with the solution, which can cause contact dermatitis
- Its antiemetic effect can mask intestinal obstruction, brain tumour or overdose of other drugs
Nursing care
- Check blood pressure before and after an injection and help the patient up slowly
- Watch for twisted neck, jaw spasm, restlessness or eye deviation after the dose
- Warn about drowsiness and falls, especially in older adults
- Ask about alcohol and other sedatives
- Teach the patient to report fever, sore throat or yellow skin
Pregnancy and breastfeeding
Newborns whose mothers received phenothiazines have shown prolonged jaundice and extrapyramidal signs; it is used only when clearly needed.
Test yourself
Think of the answer, then tap the question to see it.
Why is epinephrine avoided to treat hypotension caused by prochlorperazine?
Phenothiazines block α receptors, so epinephrine's β2 vasodilation predominates and blood pressure can fall further; norepinephrine or phenylephrine are used instead.
Why does a patient stay lying down after an intramuscular dose of prochlorperazine?
It can cause hypotension through α1-adrenergic block; the patient is observed for at least half an hour.
Which receptor explains prochlorperazine's antiemetic effect?
The dopamine D2 receptor in the chemoreceptor trigger zone.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - PROCHLORPERAZINE EDISYLATE injection (DailyMed (U.S. National Library of Medicine), 2026); Prochlorperazine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); RCSB PDB - 6LUQ: Haloperidol bound D2 dopamine receptor structure inspired discovery of subtype selective ligands (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.