CEFALEXIN

Adults 1-4 g daily in divided doses; most infections will respond to a dosage of 500 mg every 8 hours. For skin and soft tissue infections, streptococcal pharyngitis and mild, uncomplicated urinary tract infections, the usual dosage is 250 mg every 6 hours, or 500 mg every 12 hours.

More severe infections, or those caused by less susceptible organisms may need larger doses. If daily doses greater than 4g are required other parenteral cephalosporins, in appropriate doses, should be considered. Elderly As for adults although dosage should be reduced to a daily maximum of 500mg if renal function is severely impaired (glomerular filtration rate < 10ml/min).

Children The recommended daily dosage for children is 25-50 mg/kg in divided doses. In the case of skin, soft tissue infections, streptococcal pharyngitis and mild, uncomplicated urinary tract infections, the total daily dose may be divided and administered every 12 hours.

For most infections the following schedule is suggested:

Children under 5 years: Not recommended Children 5 years and over: 250 mg every 8 hours. In severe infections, the dosage may be doubled. Clinical studies have shown that for otitis media a dosage of 75-100 mg/kg/day is required, in divided doses.

In the treatment of beta-haemolytic streptococcal infections, a therapeutic dose should be administered for at least 10 days. Route of administration Oral

Gastro-intestinal - nausea, vomiting, dyspepsia, and abdominal pain have occurred. Diarrhoea has been reported most frequently. It is rarely severe enough to warrant cessation of therapy. Colitis, including are symptoms of pseudomembranous colitis, may occur during or after treatment.

Hypersensitivity - allergies (in the form of rash, urticaria and angio-oedema) have been observed. Also erythema multiforme, Stevens-Johnson syndrome usually subside upon discontinuation of the drug, although supportive therapy may be needed in some cases.

Serum sickness-like reactions with rashes and fever have been reported. Anaphylaxis has also been reported. Haematological - eosinophilia, neutropenia, thrombocytopenia leucopenia, agranulocytosis, aplastic anaemia and haemolytic anaemia have been reported.

Slight elevations of AST and ALT have been observed. Hepatic - transient hepatitis and cholestatic jaundice have been reported rarely. Miscellaneous - other reactions have included genital and anal pruritus, genital candidiasis, vaginitis and vaginal discharge, dizziness, fatigue and headache.

Agitation, confusion, hallucinations, arthralgia, arthritis and joint disorder. Hyperactivity, nervousness, sleep disturbances and hypertonia have also been reported. Reversible interstitial nephritis has been reported rarely and toxic epidermal necrolysis have been observed rarely.

If an allergic reaction to cefalexin occurs the drug should be discontinued and the patient treated with the appropriate agents. Prolonged use of cefalexin may result in the overgrowth of non-susceptible organisms. Careful observation of the patient during therapy is essential and appropriate action should be taken should superinfection occur.

Pseudomembranous colitis (ranging in severity from mild to life-threatening) has been reported in association with use of virtually all broad -spectrum antibiotics, including macrolides, semi-synthetic penicillins and cephalosporins.

Therefore, it is essential to take this into account during diagnosis of patients who develop diarrhoea during antibiotic therapy. Mild cases of pseudomembranous colitis usually respond to drug discontinuance alone whilst in more severe cases, appropriate measures should be taken.

Cefalexin should be administered with caution in the presence of markedly impaired renal function. Careful clinical and laboratory studies should be made because safe dosage may be lower than that usually recommended. A false positive reaction for glucose in the urine may occur with Benedict’s or Fehling’s solutions or with copper sulphate test tablets.

Positive direct Coombs’ tests have been reported during treatment with cephalosporin antibiotics. In haematological studies, or in transfusion cross-matching procedures when anti globulin tests are performed on the minor side, or in Coombs’ testing of newborn babies whose mothers have received cephalosporin antibiotics before parturition, it should be noted that a positive Coombs’ test may be due to the drug.

Cefalexin is contraindicated in patients with known allergy to the cephalosporins group of antibiotics. Cefalexin is contra-indicated in patients with porphyria.