BMA Concise Guide to Medicine & Drugs


Brand names Avomine, Phenergan, Sominex

Used in the following combined preparations Night Nurse, Tixylix


Drug group Antihistamine and anti-emetic drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed No (most preparations); Yes (injection)

Available as generic Yes


Promethazine is one of a class of drugs known as the phenothiazines, which were developed in the 1950s for their beneficial effect on abnormal behaviour arising from mental illnesses (see Antipsychotics). Promethazine was found, however, to have effects more like the antihistamines used to treat allergies and some types of nausea and vomiting (see Anti-emetics). The drug is widely used to reduce itching in a variety of skin conditions including urticaria (hives), chickenpox, and eczema. It can also relieve the nausea and vomiting caused by inner ear disturbances such as Ménière’s disease and motion sickness. Because of its sedative effect, promethazine is sometimes used for short periods as a sleeping medicine, and is also given as premedication before surgery.

Promethazine is used in combined preparations together with opioid cough suppressants for the relief of coughs and nasal congestion, and it is given at night for its sedative effect.


Follow instructions on the label. Call your doctor if symptoms worsen.

How taken/used Tablets, liquid, injection.

Frequency and timing of doses Allergic symptoms 1–3 x daily or as a single dose at night. Motion sickness Bedtime on night before travelling, repeating following morning if necessary, then every 6–8 hours as necessary. Nausea and vomiting Every 4–6 hours as necessary.

Dosage range Adults 25–100mg per dose, depending on preparation and use. Children Reduced dose according to age.

Onset of effect Within 1 hour. If dose is taken after nausea has started, the onset of effect is delayed.

Duration of action 8–16 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose No cause for concern, but take as soon as you remember. Adjust the timing of your next dose accordingly.

Stopping the drug Can be safely stopped as soon as symptoms disappear.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause drowsiness or agitation, seizures, unsteadiness, and coma. Notify your doctor.


Promethazine usually causes only minor anticholinergic effects. More serious adverse effects generally occur only during long-term use or with abnormally high doses. Common adverse effects include drowsiness, lethargy, blurred vision, and urinary retention. Discuss with your doctor if you have urinary retention or if any of these other effects are severe. Less commonly, palpitations may occur; if so, consult your doctor. If you develop a light-sensitive rash, you should stop taking the drug and contact your doctor.


Pregnancy urine test Promethazine may interfere with this test, giving a false result.

Skin-prick allergen tests Promethazine should be stopped a week before skin-prick testing with allergen extracts as it may produce a false result.

Sedatives All drugs that have a sedative effect are likely to increase the sedative properties of promethazine. Such drugs include other antihistamines, benzodiazepines, opioid analgesics, and antipsychotics.


Be sure to consult your doctor or pharmacist before taking this drug if:

· You have liver or kidney problems.

· You have had epileptic seizures.

· You have heart disease.

· You have glaucoma.

· You have prostate problems.

· You have difficulty in passing urine.

· You are taking other medicines.

Pregnancy The drug is probably safe in pregnancy, although safety has not been definitively established. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.

Infants and children Not recommended for infants under two years. Reduced dose necessary for older children.

Over 60 Reduced dose may be necessary.

Driving and hazardous work Avoid such activities until you have learned how promethazine affects you because the drug can cause drowsiness.

Alcohol Avoid. Alcohol may increase the sedative effects of this drug.

Sunlight and sunbeds Avoid exposure to strong sunlight because, rarely, skin reactions may occur.


Use of this drug for long periods is rarely necessary.