SPL Set ID: 445b2a87-2e4f-483a-abe8-26fefd67514a

Cephalexin tablets, USP contain the active ingredient cephalexin, which is a semisynthetic cephalosporin antibiotic intended for oral administration. It is 7-(D-α- amino-α-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid, monohydrate. Cephalexin, USP has the molecular formula C 16 H 17 N 3 O 4 S•H 2 O and the molecular weight is 365.40. Cephalexin, USP has the following structural formula: The nucleus of cephalexin is related to that of other cephalosporin antibiotics. The compound is a zwitterion; i.e., the molecule contains both a basic and an acidic group. The isoelectric point of cephalexin in water is approximately 4.5 to 5. The crystalline form of cephalexin which is available is a monohydrate. It is a white crystalline solid having a bitter taste. Solubility in water is low at room temperature; 1 or 2 mg/mL may be dissolved readily, but higher concentrations are obtained with increasing difficulty. The cephalosporins differ from penicillins in the structure of the bicyclic ring system. Cephalexin, USP has a D -phenylglycyl group as substituent at the 7-amino position and an unsubstituted methyl group at the 3-position. Each tablet contains cephalexin monohydrate equivalent to 250 mg or 500 mg of cephalexin. The tablets also contain magnesium stearate, microcrystalline cellulose, polyethylene glycol, sodium starch glycolate, and titanium dioxide. In addition, the 250 mg contains hypromellose and polysorbate 80. The 500 mg contains polyvinyl alcohol-part hydrolyzed and talc. cephalexin structural formula