Cefalexin (Cephalexin)

How it works

It is a beta-lactam that inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins, leading to cell lysis.

Prescribing in practice

• Avoid in patients with a history of immediate or severe hypersensitivity to penicillins or cephalosporins because of cross-reactivity risk.
• Dose adjustment is required in renal impairment as the drug is largely renally excreted; follow the SPC.
• It is unreliable against Pseudomonas and many resistant Gram-negative organisms, so culture and sensitivities should guide prolonged use.

Monitoring

Routine monitoring is not needed for short courses, but renal function and clinical or microbiological response should be reviewed when used for prophylaxis or in impairment.

Counselling the patient

• Complete the prescribed course even if symptoms settle.
• Report rash, swelling, or difficulty breathing as these may signal allergy.
• Diarrhoea is common; seek advice if it is severe or persistent.

Evidence & guidelines

A long-established cephalosporin with extensive clinical use supporting its efficacy in urinary tract infection and UTI prophylaxis.