CEPHALEXIN - cephalexin capsule
Sun Pharmaceutical Industries Limited
Cephalexin Capsules, USP is a semisynthetic cephalosporin antibiotic intended for oral administration. It is 7-(D-a-Amino-a-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid monohydrate. Cephalexin has the molecular formula C16 H17 N3 O4 S•H2 O and the molecular weight is 365.41.
The nucleus of cephalexin is related to that of other cephalosporin antibiotics. The compound is a zwitterion; ie, 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.
Each capsule contains cephalexin monohydrate equivalent to 250 mg (720 ?mol) or 500 mg (1,439 ?mol) of cephalexin. The capsules also contain colloidal silicon dioxide, D & C Yellow No. 10, FD & C Blue No. 2, gelatin, magnesium stearate, sodium starch glycolate, and titanium dioxide.
Cephalexin is acid stable and may be given without regard to meals. It is rapidly absorbed after oral administration. Following doses of 250 mg, 500 mg, and 1 g, average peak serum levels of approximately 9, 18, and 32 mcg/mL respectively were obtained at 1 hour. Measurable levels were present 6 hours after administration. Cephalexin is excreted in the urine by glomerular filtration and tubular secretion. Studies showed that over 90% of the drug was excreted unchanged in the urine within 8 hours. During this period, peak urine concentrations following the 250-mg, 500-mg, and 1-g doses were approximately 1,000, 2,200, and 5,000 mcg/mL respectively.
In vitro tests demonstrate that the cephalosporins are bactericidal because of their inhibition of cell-wall synthesis. Cephalexin has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.
Staphylococcus aureus (including penicillinase-producing strains)
Streptococcus pneumoniae (penicillin-susceptible strains)
Moraxella (Branhamella) catarrhalis
Note –Methicillin-resistant staphylococci and most strains of enterococci (Enterococcus faecalis [formerly Streptococcus faecalis ]) are resistant to cephalosporins, including cephalexin. It is not active against most strains of Enterobacter spp., Morganella morganii , and Proteus vulgaris. It has no activity against Pseudomonas spp. or Acinetobacter calcoaceticus. Penicillin-resistant Streptococcus pneumoniae is usually cross-resistant to beta-lactam antibiotics.