Antibiotics are not an alternative to surgical drainage and should only be used as an adjunctive treatment for patients with the following:

  • Significant peri-anal cellulitis
  • Diabetes or other significant immunocompromise
  • Sepsis

See here if Fournier’s gangrene suspected.

Recommended total duration: Stop 24 hours after surgical drainage.

Required Investigations

  • Collect pus in a universal container for culture during incision and drainage of the abscess
  • Send a swab only if you cannot collect pus in a sample container
  • Blood cultures if febrile or evidence of sepsis.

Recommended antibiotics

Recommended total duration: Stop 24 hours after surgical drainage.

  •  If cellulitis present 5 days (total duration = IV + oral)
Recommended antibiotics

Flucloxacillin  2g every 6 hours IV

PLUS

Gentamicin (use NHS Lothian Calculator AMT intranet page)

PLUS

Metronidazole  400mg every 8 hours orally (or 500mg every 8 hours IV if oral route unavailable)
Penicillin-allergy OR previous MRSA

Vancomycin  IV (use NHS Lothian Calculator AMT intranet page) - target trough level 10-15mg/L

PLUS

Gentamicin IV (use NHS Lothian Calculator AMT intranet page)

PLUS

Metronidazole 400mg every 8 hours orally (or 500mg every 8 hours IV if oral route unavailable)

 

IV to oral switch

Preferred

Co-trimoxazole 960mg every 12 hours orally

PLUS

Metronidazole 400mg every 8 hours orally
Alternative

Co-amoxiclav 625mg every 8 hours orally

Suitable for those ≤ 65 years old with a low risk of C.diff infection.

See Prevention, diagnosis and management of CDI

Notes

Likely organisms: Bacteroides, Staphylococcus aureus, Streptococcus spp., E.coli

  • Metronidazole has excellent oral bioavailability – only give IV in severe illness, suspected malabsorption or oral route compromised.
  • Dual-anaerobe cover: adding Metronidazole to Co-amoxiclav: is not usually required.