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Promethazine hydrochloride is a racemic compound.

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

C₁₇H₂₀N₂S•HCl           M.W.320.88

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

Each tablet, for oral administration, contains 25 mg or 50 mg of promethazine hydrochloride. In addition each tablet contains the following inactive ingredients: dibasic calcium phosphate, magnesium stearate, microcrystalline cellulose, sodium starch glycolate and stearic acid.

Promethazine Hydrochloride Tablets USP, 50 mg also contain anhydrous lactose.

Last reviewed on RxList: 6/13/2008
This monograph has been modified to include the generic and brand name in many instances.