Compazine is the brand name for prochlorperazine, a phenothiazine-derived medication that acts primarily as an antiemetic. In Hong Kong, it is a prescription-only (Rx) product supplied as a 5 mg oral pill. While its pharmacological class places it among antipsychotics, its most common therapeutic application is the relief of nausea and vomiting, a symptom frequently encountered in digestive health care. The Hong Kong Department of Health’s Pharmacy and Poisons Board authorises its use for these indications.
Prochlorperazine blocks dopamine D₂ receptors in the chemoreceptor trigger zone of the brain, reducing the neural signals that provoke nausea and vomiting. It also exhibits antagonism at histamine H₁, muscarinic acetylcholine, and α-adrenergic receptors, which contributes to its sedative and anticholinergic side-effect profile.
By dampening dopaminergic activity, Compazine interrupts the reflex arc that leads to emesis, making it effective for nausea caused by chemotherapy, postoperative recovery, and gastro-intestinal disorders.
Compazine is approved in Hong Kong for the following indications:
Although prochlorperazine is also listed for certain psychiatric conditions (e.g., schizophrenia) in other jurisdictions, the primary digestive-health focus in Hong Kong is its antiemetic role.
Some clinicians use prochlorperazine off-label for:
These applications are not approved by the Hong Kong regulatory authorities. Off-label use requires careful medical supervision, consideration of fetal risk in pregnancy, and monitoring for extrapyramidal side effects.
Patients with a personal or family history of QT prolongation, tardive dyskinesia, or neuroleptic malignant syndrome (NMS) should discuss alternative therapies with their prescriber.
If any of the above serious symptoms occur, seek emergency medical care.
Patients should provide a complete medication list, including over-the-counter products and herbal supplements, to their healthcare provider before starting Compazine.
Dosage must be individualized by a qualified prescriber, especially for patients with renal or hepatic impairment.
This article provides educational information about Compazine (prochlorperazine) and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Alcohol can increase the sedative effects of prochlorperazine, leading to enhanced drowsiness and dizziness. It is advisable to limit or avoid alcohol while taking the medication.
Take the missed tablet as soon as you remember, unless it is almost time for your next scheduled dose. In that case, skip the missed dose and continue with your regular dosing schedule-do not double the dose.
Compazine is classified as a Category C drug in pregnancy, meaning risk cannot be ruled out. It should only be used if the potential benefit justifies the potential risk to the fetus, and only under close medical supervision.
Compazine primarily blocks dopamine receptors, whereas ondansetron blocks serotonin 5-HT₃ receptors. This difference can affect side-effect profiles and suitability for specific causes of nausea.
Key signs include high fever, severe muscle rigidity, rapid heart rate, unstable blood pressure, and altered mental status. Prompt medical attention is essential if these symptoms appear.
Yes. Anticholinergic activity can reduce gastrointestinal motility, leading to constipation. Maintaining adequate fluid intake and dietary fiber can help mitigate this effect.
An ECG is not required for every patient, but it is recommended for individuals with existing heart disease, electrolyte imbalances, or those taking other QT-prolonging medications.
Long-term use should be regularly reviewed by a healthcare professional. Prolonged therapy increases the risk of extrapyramidal symptoms and tardive dyskinesia.
Sit or lie down immediately to avoid falls, and avoid driving or operating machinery until the dizziness resolves. Contact your prescriber if the symptom persists or worsens.
Store the pills at room temperature, away from moisture and direct sunlight, and keep them out of reach of children. Do not use tablets if the packaging is damaged.
