Intra-abdominal sepsis including hepatobiliary (Antimicrobial)
TAM (Treatments and Medicines) NHS Highland
What's new / Latest updates
28/09/26 V3: reviewed and approved by AMT 10/09/26
- a new recommendation in non-severe penicillin allergy has been added to use cefuroxime plus metronidazole.
- Due to high oral bioavailability, metronidazole should now be prescribed routinely via the oral route unless nil by mouth due to obstruction or severe sepsis. Similar advice is given for ciprofloxacin.
- Total duration of therapy is confirmed as IV plus oral.
- Revised advice is given for treatment of infections arising withing 24 hours of surgery where gentamicin has been given as prophylaxis.
12/08/26 v2.3:
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Changed: 'Note, due to high oral bioavailability, metronidazole can be given orally as soon as the oral route is established.' to 'Note, oral route preferred for metronidazole if able to take oral medication, IV only required if nil by mouth (eg obstruction) or severe sepsis. Note "sip til send" policy allows oral medication with water up until time of surgery.'
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1st Line changed:
PLUS IV metronidazole 500mg 3 times daily - see note about early switch to oral metronidazole
to:
PLUS oral metronidazole 400mg 3 times daily
OR IV metronidazole 500mg 3 times daily (if nil by mouth due to obstruction or severe sepsis).
Timely administration in sepsis is vital, ensure agents covering gram negative pathogens (gentamicin, cefuroxime or ciprofloxacin) are given first.
In severe illness, unresponsive to first-line therapy, contact Microbiologist for advice.
Note, oral route preferred for metronidazole if able to take oral medication, IV only required if nil by mouth (eg obstruction) or severe sepsis. Note "sip til send" policy allows oral medication with water up until time of surgery.
For infections arising within 24 hours of surgery where gentamicin has been given as part of surgical prophylaxis: check gentamicin level. If <1mg/l, start treatment dose gentamicin as per NHS Highland gentamicin guidelines. If 1mg/l or higher, switch to non-severe penicillin allergy recommendation (cefuroxime plus metronidazole) or, in severe penicillin allergy, substitute gentamicin for ciprofloxacin (dose as per table below).
For glossary of terms see Glossary.
Drug details
First Line:
See ward poster for sequence of drug administration
IV gentamicin - refer to NHS Highland gentamicin guidelines
PLUS IV amoxicillin 1g every 8 hours
PLUS oral metronidazole 400mg 3 times daily
OR IV metronidazole 500mg every 8 hours (if nil by mouth due to obstruction or severe sepsis)
7 to 10 days (total IV + oral)
For infections arising within 24 hours of surgery where gentamicin has been given as part of surgical prophylaxis : check gentamicin level. If <1mg/l, start treatment dose gentamicin as per NHS Highland gentamicin guidelines. If 1mg/l or higher, switch to non-severe penicillin allergy recommendation (cefuroxime plus metronidazole) or substitute gentamicin for ciprofloxacin (dose as per severe penicillin allergy).
First line if non-severe penicillin allergy
IV cefuroxime 1.5 grams every 8 hours
PLUS oral metronidazole 400mg 3 times daily
OR IV metronidazole 500mg every 8 hours (if nil by mouth due to obstruction or in severe sepsis)
First line if severe penicillin allergy (eg anaphylaxis, severe cutaneous reaction (SCAR))
IV ciprofloxacin 400mg IV every 8 hours (if nil by mouth, eg obstruction or in severe sepsis) otherwise 750mg oral twice daily (see BNF warnings and MHRA Drug Safety Alert (updated 22 January 2024))
PLUS IV vancomycin - refer to NHS Highland vancomycin guidelines
PLUS oral metronidazole 400mg 3 times daily
OR IV metronidazole 500mg every 8 hours (if nil by mouth due to obstruction or in severe sepsis)
Where vancomycin cannot be used, substitute with teicoplanin and follow the doses for use in infections with sepsis.
Oral step down
If a pathogen has been isolated, therapy should be targeted against that organism with advice from Microbiology as necessary.
If no positive Microbiology result
Oral co-trimoxazole 960mg twice daily
PLUS oral metronidazole 400mg 3 times daily
7 to 10 days (total IV + oral)
Cautions for co-trimoxazole use: in renal impairment or in combination with other drugs which promote hyperkalaemia, monitor potassium levels if used for longer than 3 days.
In renal impairment (CrCl 30ml/min or less)
Oral co-trimoxazole 480mg twice daily
PLUS oral metronidazole 400mg three times daily
7 to 10 days (total IV + oral)
Cautions for co-trimoxazole use: in renal impairment or in combination with other drugs which promote hyperkalaemia, monitor potassium levels if used for longer than 3 days.