ALLEGRA-D® 12 HOUR (fexofenadine hydrochloride and pseudoephedrine hydrochloride) Extended-Release Tablets for oral administration contain 60 mg fexofenadine hydrochloride for immediate release and 120 mg pseudoephedrine hydrochloride for extended release. Tablets also contain as excipients: microcrystalline cellulose, pregelatinized starch, croscarmellose sodium, magnesium stearate, carnauba wax, stearic acid, silicon dioxide, hypromellose and polyethylene glycol.

Fexofenadine hydrochloride, one of the active ingredients of ALLEGRA-D 12 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 12 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. 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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