The most important pharmacological feature of promethazine is its strong antihistamine (H1-blocking) activity. Prometazine is well absorbed when administered orally. With different routes of administration it penetrates through the blood-brain barrier. The drug has a pronounced effect on the CNS; it has a fairly strong sedative activity, enhances the effect of narcotic, sedative, analgesic and local anesthetic drugs, lowers body temperature, prevents and calms vomiting. It also has a moderate peripheral and central cholinolytic effect. The adrenolytic effect of promethazine is strongly pronounced.
Simultaneous use of promethazine potentiates the effect of opioid analgesics, hypnotics and local anaesthetics. Simultaneous use of promethazine with tricyclic antidepressants may increase the m-cholinoblocking effect as well as the CNS depressant effect; with antihypertensive drugs, the effects of the latter may be enhanced.
Promethazine is used in treatment of allergic diseases (urticaria, serum sickness, hay fever, etc.). ), in vasomotor and allergic rhinitis, in rheumatism with a pronounced allergic component, in allergic complications caused by penicillin, streptomycin and other drugs, as well as in itching dermatosis, Meniere’s disease, chorea, encephalitis and other CNS diseases accompanied by increased vascular permeability, in sea and air disease. In surgical practice promethazine is used as one of the main components of lytic mixtures (see Aminazin) used for potentiated anesthesia and hypothermia, for prevention and reduction of postoperative complications, during surgery and in the postoperative period. It is also used to enhance the effect of analgesics and local anesthetics.
Histamine H1-receptor blocker, phenothiazine derivative. It has a pronounced antihistamine activity and has a significant effect on the CNS (has sedative, hypnotic, antiemetic, antipsychotic and hypothermic effects). It prevents and calms hiccups. Prevents histamine-mediated effects (including urticaria and itching). Anticholinergic action causes a drying effect on the mucous membranes of the nose and mouth. The antiemetic effect of promethazine is due to its central anticholinergic effect, decrease in excitability of the vestibular system, suppression of labyrinthine function and direct inhibitory effect on trigger chemoreceptor zones of medulla oblongata.
The sedative effect is due to inhibition of histamine-K-methyltransferase and blockade of central histamine receptors. Blockade of other CNS receptors such as serotonin and choline receptors is also possible; stimulation of α-adrenoreceptors indirectly attenuates stimulation of the reticular formation of the brain stem.