Each teaspoon (5 mL) of Promethazine HCl and Dextromethorphan Hydrobromide Syrup contains 6.25 mg promethazine HCl and 15 mg dextromethorphan hydrobromide in a flavored syrup base with a pH between 4.7 and 5.2. Alcohol 7%. The inactive ingredients present are artificial and natural flavors, citric acid, D&C Yellow 10, FD&C Yellow 6, glycerin, saccharin sodium, sodium benzoate, sodium citrate, sodium propionate, water, and other ingredients.

Promethazine HCl is a racemic compound; the empirical formula is C₁₇H₂₀N₂S•HCl and its molecular weight is 320.88.

Promethazine HCl, a phenothiazine derivative, is chemically designated as 10H-Phenothiazine-10- ethanamine, N,N, α-trimethyl-, monohydrochloride, (±)- with the following structural formula:

Promethazine HCl occurs as a white to faint yellow, practically odorless, crystalline powder which slowly oxidizes and turns blue on prolonged exposure to air. It is freely soluble in water and soluble in alcohol.

Dextromethorphan hydrobromide is a salt of the methyl ether of the dextrorotatory isomer of levorphanol, a narcotic analgesic. It is chemically designated as 3-methoxy-17-methyl-9α, 13α, 14α– morphinan hydrobromide monohydrate with the following structural formula:

Dextromethorphan hydrobromide monohydrate occurs as white crystals, is sparingly soluble in water, and is freely soluble in alcohol. The empirical formula is C₁₈H₂₅NO•HBr•H2O, and the molecular weight of the monohydrate is 370.33. Dextromethorphan HBr monohydrate is dextrorotatory with a specific rotation of +27.6 degrees in water (20 degrees C, sodium D-line).

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