It is used for symptomatic treatment of allergic diseases. Earlier it was also used for potentiation of anesthesia. Promethazine is used in the treatment of allergic diseases, 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 diseases of CNS accompanied by increased vascular permeability, in sea and air illness. In surgical practice promethazine is used as one of the main components of lytic mixtures 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.
Promethazine is usually well tolerated. When administered orally it may cause moderate anesthesia of the oral mucosa; dry mouth and nausea sometimes occur. When administered intramuscularly, painful infiltrates may occur. When administered intravenously, blood pressure sometimes decreases severely. Promethazine should be used with caution in persons with impaired hepatic and renal function. Due to strengthening of narcotic action the drug should be used with caution in persons under the influence of alcohol. Do not drink alcoholic beverages during treatment with Promethazine.
Promethazine should not be prescribed for itching and other allergic reactions caused by the use of phenothiazine drugs aminazine and others because promethazine itself is a drug of this chemical group. Because of its sedative effect, Prometazine should not be prescribed for drivers and other persons whose occupation requires rapid mental and motor reactions. Note. Promethazine has an irritant effect and may cause dermatitis and irritation of mucous membranes. The same precautions as for aminazin shall be observed when handling promethazine.
The most important pharmacological feature of promethazine is its strong antihistamine H1-blocking activity. Promethazine is well absorbed when taken 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.
It potentiates the effects of narcotic analgesics, hypnotics, anxiolytics (tranquilizers) and antipsychotic drugs (neuroleptics) as well as anesthetics, local anesthetics, m-cholinoblockers and hypotensive drugs (dose adjustment required). It reduces the effect of amphetamine derivatives, m-cholinostimulants, anticholinesterase drugs, ephedrine, guanethidine, levodopa, dopamine. Barbiturates accelerate elimination and decrease activity. Beta-adrenoblockers increase (mutually) plasma concentrations (pronounced BP decrease, arrhythmias, irreversible retinopathy, tardive dyskinesia are possible). It weakens the effect of bromocriptine and increases the serum concentration of prolactin.
Tricyclic antidepressants and anticholinergic drugs increase m-cholinoblocking activity, ethanol, clopheline, antiepileptic drugs – CNS depression. MAO inhibitors (concomitant use is not recommended) and phenothiazine derivatives increase the risk of arterial hypotension and extrapyramidal disorders. Quinidine increases the likelihood of cardiodepressive effects. Myelotoxic drugs increase the manifestation of hematotoxicity of the drug.