The drug of phenothiazine series, has high antihistamine activity and pronounced effect on CNS. It has sedative, hypnotic, antiemetic, antipsychotic and hypothermic effects. It prevents and calms hiccups. Promethazine prevents but does not eliminate histamine-mediated effects (including urticaria and pruritus). Anticholinergic action causes a drying effect on the mucous membranes of the nasal and oral cavities. The anti-emetic, dizziness-relieving effect may be due to the central anticholinergic action. It reduces vestibular receptor stimulation and inhibits labyrinth function. The antiemetic effect may be due to action on the chemoreceptor trigger zone of the medulla oblongata. Sedative action is due to inhibition of histamine-N-methyltransferase and blockade of central histaminergic receptors. Blockade of other CNS receptors such as acetylcholine receptors is also possible, stimulation of alpha-adrenergic receptors indirectly weakens stimulation of the brainstem reticular formation.
Dosage and administration
Orally (after meals), rectally, intravenously, intravenously. Adults: 12.5-25 mg 3-4 times during the daytime and 25-50 mg at night (maximum doses: single dose – 75 mg, daily – 500 mg). In kinetosis, 12.5-25 mg 3-4 times daily orally. In case of nausea and vomiting, at first 25 mg, then 12.5-25 mg every 4-6 hours. For children: 2-6 years of age – 12.5 mg, 6-14 years – 25 mg 3-4 times a day. Parenterally (emergency cases, anesthesia): intravenously (deep into the muscle) in a dose of 0.5-1 mg/kg 3-5 times a day (in severe cases, the initial dose is 1-2 mg/kg), the maximum daily dose is 250 mg; intravenously (for hibernation) 0.15-0.3 mg/kg (maximum concentration) – 25 mg/ml, the rate of administration is 25 mg/min). In preparation for surgery, the night before – 25-50 mg orally along with other drugs; on the day of surgery 2.5 hours before surgery – 50 mg/m (in combination with analgesic and cholinolytic), possible to be repeated in 1 hour; in children, the dose is 1.1 mg/kg. For seasickness syndrome prophylaxis, once 1 hour before travel, adults 25-50 mg, children 10-20 mg. For adjuvant therapy of anaphylactic shock – 10-20 mg intravenously slowly (after epinephrine injection) and further during the next 24-48 hours to prevent relapse.
May suppress the cough reflex, so caution is necessary in patients (especially children) with exacerbation of chronic respiratory diseases. Caution should be used in patients with liver dysfunction, cardiovascular system diseases and bone marrow hematopoiesis suppression. In the elderly, caution is required when parenteral administration of high doses, because extrapyramidal disorders and acute urinary retention are possible. In case of long-term use, peripheral blood cell composition should be periodically monitored. As an antiemetic agent it should be used only in case of prolonged vomiting of known etiology. Caffeine administration is recommended to prevent CNS depression. Long-term use increases the risk of dental disease (caries, periodontitis, candidiasis) due to reduced salivation. May mask the ototoxic effect (tinnitus and dizziness) of co-administered drugs. Increases the need for riboflavin. It should not be used for drivers of vehicles and people with professions connected with high concentration (especially at the beginning of the course). It is necessary to exclude alcohol consumption during treatment.