Severe peri-anal infection (requires urgent surgical review)

Co-amoxiclav IV 1.2g 8 hourly

If eGFR 10-20ml/minute/1.73m²:

Temocillin IV 2g every 24 hours

and

Metronidazole oral 400mg 8 hourly

If eGFR <10ml/minute/1.73m²:

Temocillin IV 2g every 48 hours

and

Metronidazole oral 400mg 8 hourly

If true penicillin / beta-lactam allergy:

Metronidazole oral 400mg 8 hourly

and

Clindamycin IV 600mg 6 hourly

and

Gentamicin* IV (dosing info here)

Total course duration (IV and oral): 10 days.

*Gentamicin – Do not continue gentamicin beyond 3–4 days unless on the advice of microbiology / infectious diseases unit. If you are unsure whether >4 days is needed, contact an infection specialist.