Cephalexin
Cephalexin is a semisynthetic analogue of Cephalosporin C. It kills bacteria by interfering in the synthesis of the bacterial cell wall. Peptidoglycan is a heteropolymeric structure that provides the cell wall with mechanical stability. The final stage in the synthesis of peptidoglycan involves the completion of the cross-linking and the terminal glycine residue of the Pentaglycine Bridge is linked to the fourth residue of the pentapeptide (d-alanin). The transpeptidase enzyme that performs this step is inhibited by penicillins and cephalosporins. As a result the bacterial cell wall is weakened, the cell swells and then ruptures. Cephalexin is a first generation cephalosporin that is active by mouth.
Adult:The usual dose is 250 mg to 500 mg every 6 hour.For skin and soft tissue infections, streptococcal pharyngitis and uncomplicated cystitis, in patients over 15 years of age: 500 mg of the drug may be administered every 12 hour.In severe or deep seated infections the dose can be increased up to 3 g to 6 g daily.Children: The dosage range is 25-100 mg/kg/day in divided doses to a maximum of 4 g dailyChildren's Weight Recommended Dose:10 kg (22 Ibs): 62.5 mg to 125 mg qid or 125 mg to 250 mg bid20 kg (44 Ibs): 125 mg to 250 mg qid or 250 mg to 500 mg bid40 kg (88 Ibs): 250 mg to 500 mg qid or 500 mg to 1 g bidFor streptococcal pharyngitis, skin and soft tissue infections and in patients over 1 year of age the total daily dose may be divided and administered every 12 hour. In the therapy of otitis media 75-100 mg/kg/day in four divided doses may be required. In the treatment of β haemolytic streptococcal infections a therapeutic dosage of the drug should be given at least for 10 days.
Cephalen is contraindicated in patients with known hypersensitivity to the cephalosporin group of antibiotics.
Side effects include nausea, vomiting, diarrhoea and abdominal discomfort. Symptoms of pseudomembranous colitis may appear either during or after antibiotic treatment. Skin rash, angio oedema, rise in serum aminotransferases, eosinophilia, neutropenia have been reported very rarely. Superinfection with resistant micro organisms, particularly candida may follow the treatment.
Pregnancy Category B. Cefalexin may be used during pregnancy when it is considered essential. Cefalexin is found in the milk of nursing mothers, hence caution should be taken when it is administered to nursing mothers.
Cefalexin should be given with caution in patients with renal impairment. Under such condition, careful clinical observation should be made because safe dosage may be lower than the usually recommended. The urine of patients receiving Cefalexin may give a false positive reaction for glucose with copper reduction reagent. Positive results to Coombs’ test have been reported. Although there is no evidence of teratogenicity in animal tests, Cefalexin may be used during pregnancy when it is considered essential. Cefalexin is found in the milk of nursing mothers, hence caution should be taken when it is administered to nursing mothers.
First generation Cephalosporins
Should be stored in cool and dry place.
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