To reduce the development of drug-resistant bacteria and maintain the effectiveness of Cephalexin for Oral Suspension USP and other antibacterial drugs, Cephalexin for Oral Suspension, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

DESCRIPTION

Cephalexin, USP 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 has the molecular formula C16H17N3O4S•H2O and the molecular weight is 365.41. 
    Cephalexin 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 has a D-phenylglycyl group as substituent at the 7-amino position and an unsubstituted methyl group at the 3-position.

After mixing, each 5 mL of Cephalexin for Oral Suspension, USP, will contain cephalexin monohydrate equivalent to 125 mg (360 µcmol) or 250 mg (720 µcmol) of cephalexin. The suspensions also contain citric acid, guarana flavour, sodium saccharin, sucrose, xanthan gum. The 125-mg suspension contains FD&C Red No.40, and the 250-mg suspension contains FD&C Yellow No. 6.

CLINICAL PHARMACOLOGY