This 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. Prevents, but does not eliminate, histamine-mediated effects (including urticaria and itching). Anticholinergic action causes a drying effect on the mucous membranes of the nasal and oral cavities. The anti-emetic, dizziness-relieving effect promethazine 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 brainstem reticular formation stimulation. Clinical effect begins to develop when administered orally – after 15-60 min, when administered intravenously – after 20 min, when administered intravenously – 3-5 min and lasts for 6, sometimes 12 hours.
It is quickly and well absorbed from the gastrointestinal tract. During different routes of administration it penetrates through the BBB (accumulates in CNS in significant concentrations) and placental barrier. Binding with plasma proteins is 65-90%. Metabolized in the liver to form sulfoxides and demethylated promethazine derivatives. T1/2 when taken orally is 7-14 hours. It is eliminated mainly by the kidneys and to a lesser extent in the bile.
Allergic diseases (rash, rheumatism with a strong allergic component, prurigo, eczema, exudative diathesis, drug rash, serum sickness, angioedema, hay fever, bronchial asthma, anaphylactic shock, rheumatism with a strong allergic component, insect bites),
gastric secretion study (to prevent complications when used as a stimulant for histamine secretion).
In anesthesiology: premedication, postoperative period, as a component of lytic mixtures used to enhance general anesthesia and hypothermia, the effect of analgesics and local anesthetics; in artificial hibernation.
In neurology: kinetosis, to reduce extrapyramidal disorders when using antipsychotic drugs (neuroleptics), chorea, encephalitis, etc. CNS diseases accompanied by increased vascular permeability; alcohol delirium, trigeminal neuralgia, Meniere’s syndrome, dizziness, nausea and vomiting, hyperthermia during poisoning, sea and air sickness, psychosis, neurosis (agitation, anxiety, sleep disorders) – as part of complex therapy.
In pediatrics: changes in the skin and mucous membranes in infants against exudative diathesis, eczema, asthmatic bronchitis, false croup, allergic dermatitis, serum sickness.
Hypersensitivity (including to other phenothiazines), concomitant use of MAO inhibitors, lactation, early childhood (under 3 months).
Caution. Bladder neck obstruction, prostatic hypertrophy with clinical manifestations, predisposition to urinary retention, epilepsy, open-angle or closed-angle glaucoma, coma, liver failure, Jaundice, bone marrow dysfunction, diseases of the CSS (severe angina, arterial hypertension, decompensated CHF, atrial fibrillation), Reye syndrome, pregnancy, children (under 2 years) and elderly.