ALLEGRA-D® 24 HOUR (fexofenadine hydrochloride and pseudoephedrine hydrochloride) Extended-Release Tablets for oral administration contain 180 mg fexofenadine hydrochloride for immediate release and 240 mg pseudoephedrine hydrochloride for extended release. Tablets also contain as excipients: microcrystalline cellulose, sodium chloride, cellulose acetate, polyethylene glycol, opadry white, povidone, talc, hypromellose, croscarmellose sodium, copovidone, titanium dioxide, magnesium stearate, colloidal silicon dioxide, brilliant blue aluminum lake, acetone, isopropyl alcohol, methyl alcohol, methylene chloride, water, and black ink.

Fexofenadine hydrochloride, one of the active ingredients of ALLEGRA-D 24 HOUR, is a histamine H1-receptor antagonist with the chemical name (±)-4-[1-hydroxy-4-[4- (hydroxydiphenylmethyl)-1-piperidinyl]-butyl]-α, α-dimethyl benzeneacetic acid hydrochloride and the following chemical structure:

The molecular weight is 538.13 and the empirical formula is C32H39NO4·HCl. Fexofenadine hydrochloride is a white to off-white crystalline powder. It is freely soluble in methanol and ethanol, slightly soluble in chloroform and water, and insoluble in hexane. Fexofenadine hydrochloride is a racemate and exists as a zwitterion in aqueous media at physiological pH.

Pseudoephedrine hydrochloride, the other active ingredient of ALLEGRA-D 24 HOUR, is an adrenergic (vasoconstrictor) agent with the chemical name [S-(R*,R*)]-α-[1- (methylamino)ethyl]-benzenemethanol hydrochloride and the following chemical structure:

The molecular weight is 201.70 and the molecular formula is C10H15NO•HCl. Pseudoephedrine hydrochloride occurs as fine, white to off-white crystals or powder, having a faint characteristic odor. It is very soluble in water, freely soluble in alcohol, and sparingly soluble in chloroform.

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