(1989; 60 pages) [French]
Tablet: 10 mg, 25 mg (hydrochloride)
Elixir or syrup: 5 mg (hydrochloride) in 5 ml
Injection: 25 mg (hydrochloride)/ml in 2-ml ampoule
Promethazine is an antihistaminic and sedative phenothiazine derivative with antiemetic and anticholinergic properties. It acts for about 12 hours following oral administration and is excreted in the urine, largely as metabolites, within 24 hours.
Premedication prior to surgical anaesthesia and sedation in obstetrics.
Dosage and administration
Adults: 25 mg i.m. 1 hour prior to induction.
Children over 1 year: 0.5-1 mg/kg orally as syrup or tablet, 1 hour prior to induction.
• Known hypersensitivity to promethazine or to other phenothiazine derivatives (since cross-sensitivity may occur).
• Age under 1 year.
• Impaired consciousness due to cerebral depressants or of other origin.
Ambulatory patients should be warned that promethazine may impair their ability to drive or operate machinery for up to 24 hours.
Use in pregnancy and lactation
Promethazine should be used in pregnancy only when the need outweighs any potential risk to the fetus. Sufficient promethazine is excreted in maternal milk to sedate breast-fed infants.
Adverse effects, which occur less frequently than with other phenothiazines, are usually referable to gastrointestinal irritation, allergic phenomena and dose-related central and anticholinergic effects.
Gastrointestinal effects include anorexia, nausea, vomiting, epigastric distress, constipation and diarrhoea. They may be attenuated by taking the drug with meals.
Allergic phenomena include urticaria and dermatitis. Agranulocytosis is very rare. Cholestatic jaundice, which is usually reversible on withdrawal of treatment, has been reported.
Central effects include sedation, dizziness, fatigue, insomnia, nightmares, hallucinations, nervousness, tremor, tinnitus, incoordination, diplopia and blurred vision.
Anticholinergic effects include dryness of the mouth, urinary frequency and palpitations.
The sedative effect of alcohol and other cerebral depressants is augmented.
Concurrent use of epinephrine may result in hypotension and tachycardia due to partial adrenergic blockade.
Serious poisoning is characterized by muscular twitching, convulsions, restlessness, irritability, confusion, hallucinations and coma. Gastric lavage is of value if undertaken within a few hours of ingestion. Emetics may be ineffective. Oxygen and assisted ventilation are required in the event of respiratory depression. Seizures may be controlled with diazepam.
Promethazine should be stored in well-closed containers protected from light and should not be allowed to freeze. The syrup is less stable than the other dosage forms.