Used as an anti-allergic, antihistamine, sedative, antiemetic, antipruritic, hypnotic, and local anesthetic. Competitively blocks H1-histamine receptors, has anti-exudative, anti-allergic, anti-inflammatory effects. Reduces capillary permeability, swelling of mucous membranes, itching. Blocks alpha-adrenoreceptors, M-cholinoreceptors. Inhibits histamine-N-methyltransferase, blocks central histamine H3-receptors. Depresses CNS, has sedative, anxiolytic, antipsychotic and hypnotic effects, lowers body temperature. It reduces excitability of vestibular receptors, inhibits labyrinth function, eliminates dizziness. The antiemetic effect promethazine is due to blockade of M-receptors in the chemoreceptor zone of the vomiting center of the medulla oblongata. It penetrates through the HEB. When administered 2 weeks before delivery, it may inhibit platelet aggregation in newborns. No mutagenic effects or adverse effects on fetal development have been found in experimental studies.
It is quickly and completely absorbed from the gastrointestinal tract. It takes 15-60 min to produce effects when administered orally, 20 min after intramuscular injection, 3-5 min after intravenous injection. Duration of action is 4-6 hours (after intravenous administration – up to 12 hours). It is 65-90% bound to blood plasma proteins. It is metabolized in the liver and partially in the kidneys to form promethazine sulfoxides, N-desmethylpromethazine and other derivatives. The elimination half-life is 7-14 hours. It is eliminated mainly in the urine, including in the form of metabolites.
Allergic dermatoses, prurigo, eczema, exudative diathesis, urticaria, rash and other skin allergic reactions to drugs and chemicals, itching, allergic conjunctivitis, allergic rhinitis, pollinosis, stings of wasps, bees, scorpions, bumblebees, serum sickness, angioneurotic edema, false croup, asthmatic bronchitis, atopic bronchial asthma, anaphylactic and anaphylactoid reactions (as part of complex therapy), rheumatism with a pronounced allergic component; Meniere’s syndrome, dizziness, nausea and vomiting, motion sickness; anxiety, neurosis and neurosis-like conditions, psychosis, insomnia, extrapyramidal disorders (against the background of taking neuroleptics), trigeminal neuralgia, migraine, chorea, hyperthermia; premedication and postoperative period (as a sedative, for artificial hibernation, potentiation of anesthesia and local anesthesia), study of gastric secretion (when used as a stimulant of histamine secretion).
Hypersensitivity (including to other phenothiazines), coma, concomitant use of MAO inhibitors and the period within 14 days after completion of their administration, alcohol intoxication, hepatic and/or renal failure, pregnancy, lactation, occasional vomiting in children of unspecified genesis, early childhood under 2 months (for parenteral administration), childhood under 6 years (for oral administration). Contraindicated in pregnancy.
Jaundice, prostatic hypertrophy, predisposition to urinary retention, bladder neck stenosis, open- or closed-angle glaucoma, peptic ulcer with pyloroduodenal obstruction, lower respiratory tract diseases, bone marrow dysfunction, cardiovascular diseases (severe angina, arterial hypertension, decompensated chronic heart failure, atrial fibrillation), epilepsy, sleep apnea, Reye syndrome, advanced age.