There has been a bit of confusion about cefalexin dosing recently.  The Australian Medicines Handbook (AMH) recommends 50 mg/kg/day divided into 4 doses.  Many pharmacopoeia (e.g. the British National Formulary) recommend 50-100 mg/kg/day divided into 2-4 doses, depending on the severity of the infection.

There are studies supporting the use of tds or bd dosing, although in higher doses than we‘ve typically used.  Here are the doses recommended in our CPGs, including the recently revised Victorian Antimicrobial Guidelines:

• 33 mg/kg (500 mg) bd for UTI, impetigo
• 33 mg/kg (500 mg) tds for mild cellulitis, mild lymphadenitis, mild periorbital cellulitis (higher doses may be required)
• 33 mg/kg (1 g) tds for moderate cellulitis

45 mg/kg (1.5 g) tds for osteomyelitis/septic arthritis, pyelonephritis