Indications
Prochlorperazine Mesilate is the injectable form of prochlorperazine, a phenothiazine medicine. It is used to treat severe nausea and vomiting from various causes (including after surgery, migraine, or medicines), vertigo and dizziness caused by inner ear problems such as Meniere’s disease or labyrinthitis, and, under specialist care, acute severe psychotic symptoms or agitation. Tablet forms (usually the maleate salt) are used for similar purposes.
How It Works
Prochlorperazine blocks dopamine D2 receptors in the part of the brain that triggers vomiting (the chemoreceptor trigger zone) and also has antihistamine and anticholinergic effects. This reduces nausea, vomiting and dizziness. At higher doses, dopamine blockade in other brain areas reduces psychotic symptoms.
Dosage and Administration
The injection is given deep into a muscle (or sometimes into a vein) by a doctor or nurse, and the dose is decided by the doctor as prescribed. Patients should lie down during and after the injection because it can lower blood pressure. Once vomiting is controlled, treatment is often switched to tablets. In children it is used only on specialist advice.
Interactions
- Alcohol, opioids, sleeping pills, sedating antihistamines and anaesthetics: increased drowsiness and breathing depression.
- Medicines for high blood pressure: greater fall in blood pressure.
- Anticholinergic medicines (such as Atropine or Benzhexol): more dry mouth, constipation and confusion.
- Metoclopramide and other antipsychotics: higher risk of movement side effects and neuroleptic malignant syndrome.
- Medicines that prolong the QT interval (such as Amiodarone, Erythromycin, Methadone): risk of heart rhythm problems.
- Levodopa and other Parkinson’s medicines: effects may cancel each other.
- Lithium: risk of nerve toxicity.
Contraindications
Do not use if you are allergic to prochlorperazine or other phenothiazines, in coma or severe central nervous system depression, in bone marrow disorders, phaeochromocytoma, or in children under 2 years. Not usually recommended in Parkinson’s disease, narrow-angle glaucoma or enlarged prostate.
Side Effects
- Drowsiness, dizziness, low blood pressure on standing.
- Movement problems such as muscle spasms of the neck, face or eyes, restlessness, tremor and stiffness (more common in young people and children).
- Dry mouth, blurred vision, constipation, difficulty passing urine.
- Pain at the injection site.
- Rarely: jaundice, low white blood cell count, skin sensitivity to sunlight.
Get urgent medical help for high fever with stiff muscles, sweating and confusion (neuroleptic malignant syndrome), sudden severe muscle spasms, uncontrolled movements of the face or tongue, a very fast or irregular heartbeat, fainting, fits, fever with sore throat, yellow skin or eyes, or swelling of the face and throat.
Pregnancy and Lactation
Use in pregnancy only if the doctor considers it necessary. Babies exposed in the last 3 months may have movement or withdrawal symptoms after birth. It passes into breast milk in small amounts; the doctor will advise whether breastfeeding should continue.
Precautions and Warnings
Elderly people, especially those with dementia, are more sensitive to its side effects and have a higher risk of stroke and death with antipsychotics. Use with care in heart disease, epilepsy, liver or kidney disease, Parkinson’s disease, diabetes, myasthenia gravis and low thyroid function. It may cause drowsiness; do not drive or use machines afterwards. Avoid alcohol and strong sunlight. If vomiting lasts more than a day or two, see a doctor so the cause can be found.
Overdose
Overdose may cause deep drowsiness, low blood pressure, movement problems, fast or irregular heartbeat, fits and coma. It is treated as an emergency in hospital.
Therapeutic Class
Phenothiazine antiemetic and antipsychotic.
Storage
Hospital medicine: store ampoules below 30°C, protected from light, as directed on the pack. Do not use if the solution is discoloured. Keep out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.