Each teaspoonful (5 mL) of Promethazine HCl Oral Solution, USP contains 6.25 mg of promethazine HCl, USP in a flavored syrup base with a pH between 4.7 and 5.2. Alcohol 7%. The inactive ingredients present are alcohol, ascorbic acid, citric acid, D&C Yellow # 10, edetate disodium, FD&C Blue # 1, glycerin, methylparaben, natural and artificial banana flavor, natural and artificial fruit flavor, saccharin sodium, sodium benzoate, sodium citrate, and sucrose.
Promethazine HCl, USP is a racemic compound; the molecular formula is C17H20N2S•HCl and its molecular weight is 320.88.
Promethazine HCl USP, a phenothiazine derivative, is designated chemically as 10H-Phenothiazine-10-ethanamine, N,N, α-trimethyl-, monohydrochloride, (±)- with the following structural formula:
Promethazine is a phenothiazine derivative which differs structurally from the antipsychotic phenothiazines by the presence of a branched side chain and no ring substitution. It is thought that this configuration is responsible for its relative lack (1/10 that of chlorpromazine) of dopamine antagonist properties.
Promethazine is an H1 receptor blocking agent. In addition to its antihistaminic action, it provides clinically useful sedative and antiemetic effects.
Promethazine is well absorbed from the gastrointestinal tract. Clinical effects are apparent within 20 minutes after oral administration and generally last four to six hours, although they may persist as long as 12 hours. Promethazine is metabolized by the liver to a variety of compounds; the sulfoxides of promethazine and N-demethylpromethazine are the predominant metabolites appearing in the urine.