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Author: Admin | 2025-04-28
The management of refractory hypotension, vasopressors such as phenylephrine, levarterenol, or metaraminol may be used. Acidosis and electrolyte imbalances should be corrected.Appropriate therapy should be instituted if excessive sedation occurs; CNS stimulants that may cause seizures should be avoided. If seizures occur, treatment should not include barbiturates because these drugs may potentiate phenothiazine-induced respiratory depression. However; pentobarbital and secobarbital have been used in acute overdosage of promethazine. Hypothermia is common and sometimes difficult to control. Naloxone does not appear to reverse the depressant effects of promethazine overdosage.In some patients with acute toxicity, exchange transfusions may be useful, but hemodialysis, forced diuresis, hemoperfusion, or manipulation of urine pH is of little value in enhancing elimination of phenothiazines.PharmacologyPromethazine is a phenothiazine derivative with potent antihistaminic properties and shares the actions of the antihistamines.Although the drug can produce either CNS stimulation or CNS depression, CNS depression manifested by sedation is more common with therapeutic doses of promethazine. The precise mechanism of the CNS effects of the drug is not known. Promethazine also has antiemetic, anticholinergic, and local anesthetic effects. In contrast to most other phenothiazines, promethazine also has an antimotion sickness action, possibly as a result of a central anticholinergic effect on the vestibular apparatus and the integrative vomiting center and medullary chemoreceptive trigger zone of the midbrain. Although it has been reported that the drug has slight antitussive activity, this may result from its anticholinergic and CNS-depressant effects. In therapeutic doses, promethazine appears to have no significant effect on the cardiovascular system. Although rapid IV administration of promethazine may produce a transient fall in blood pressure, blood pressure usually is maintained or slightly elevated when the drug is given slowly.Promethazine has been reported to inhibit collagen-induced neonatal platelet aggregation in vitro and collagen-induced platelet aggregation in neonates whose mothers had received the drug during labor; however, the clinical importance of this effect is not known. Promethazine also has been reported to possibly ameliorate the effects of hemolytic disease of the newborn (erythroblastosis fetalis) when administered during pregnancy in Rh-sensitized women. The exact mechanism(s) has not been elucidated, but several mechanisms may be
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