Acute Peritonitis

Pathogens

• Common: Coliforms, anaerobes
• Other: S. milleri (especially in abscesses), S. pneumoniae (especially in nephrotic syndrome)

Drug Treatment

• Consider early switch from IV to oral antimicrobials.
• Do not give gentamicin for more than 72 hours, or ciprofloxacin (IV or oral), unless on Infectious Diseases/Clinical Microbiology advice (document this in the clinical notes and/or drug chart).
• If patient fails to respond, consult Infectious Diseases/Clinical Microbiology.
• Duration:
  • 5 to 10 days.
  • Abscesses should be drained and may require longer therapy.

Empiric

Perforated viscus

cefuroxime HMLSchedNZFPMLnoids Cefuroxime F: 0.4 Half life: 2 hours Elimination: renal fe: 0.9

IV 1.5 g every eight hours

• fe = 0.9, consider adjusting dose if CrCl is reduced.

AND

metronidazole HMLSchedNZFPMLnoids Metronidazole F: 1 Half life: 8 hours Elimination: oxidation, glucuronidation fe: 0.1

PO 600 mg twice a day, or IV 500 mg every twelve hours

• High oral availability – prescribe orally unless GI absorption is compromised or patient is nil by mouth.
• Metabolised by unknown pathways. (fe = 0.1).

Severe disease (e.g. sepsis), add to the above:

gentamicin HMLSchedNZFPMLnoids Gentamicin F: n/a Half life: 3 hours Elimination: renal fe: 0.9 Additional points: TDM.

IV 5 to 7 mg/kg ideal body weight initially. See dosing guidelines

• fe = 0.9, adjust dose if CrCl reduced.
• Consult Infectious Diseases / Clinical Microbiology if more than 72 hours' treatment is required.

Follow IV therapy with

amoxicillin+clavulanic acid HMLSchedNZFPMLnoids Amoxicillin+Clavulanic Acid F: 0.9 / 0.5 Half life: 2 hours / 1 hour Elimination: renal fe: 0.9 / 0.5

PO 500 mg/125 mg three times a day

• fe (amoxicillin) = 0.9, fe (clavulanic acid) = 0.5, consider adjusting dose if CrCl reduced.

OR (if mild penicillin allergy)

• fe = 0.9, consider adjusting dose if CrCl is reduced.
• Cefuroxime is not funded for this indication on prescription – ask your ward pharmacist to supply on discharge.

AND

• Metabolised by unknown pathways. (fe = 0.1).

Severe penicillin allergy

Initiate antimicrobial therapy and consult with infectious Diseases/Clinical Microbiology.

• fe = 0.9, adjust dose if CrCl reduced.
• Consult Infectious Diseases / Clinical Microbiology if more than 72 hours' treatment is required.

AND

clindamycin HMLSchedNZFPMLnoids Clindamycin F: 0.9 Half life: 3 hours Elimination: CYP3A fe: 0.1

IV 600 mg every eight hours

• Metabolised by CYP3A. (fe < 0.1).

Follow IV therapy with

trimethoprim+sulfamethoxazole HMLSchedNZFPMLnoids Trimethoprim+Sulfamethoxazole F: 0.8 Half life: 9 hours / 12 hours Elimination: CYP2C8/9 acetylated fe: 0.3 / 0.7 (co-trimoxazole)

PO 160 mg/800 mg twice a day

• fe (trimethoprim) = 0.7, fe (sulfamethoxazole) = 0.3, consider adjusting dose if CrCl reduced.
• Sulfamethoxazole is metabolised by CYP2C8/9 and conjugation.

AND

• Metabolised by unknown pathways. (fe = 0.1).

Patients unresponsive to treatment or requiring IV therapy for more than 72 hours

Consult Infectious Diseases/Clinical Microbiology.

Pathogens Known

S. milleri

benzylpenicillin HMLSchedNZFPMLnoids Benzylpenicillin F: n/a Half life: 1 hour Elimination: hydrolysis fe: 0.9 (Penicillin G)

IV 1.2 g (2 megaunits) every four hours

• fe = 0.8, consider adjusting dose if CrCl is reduced.

Mild penicillin allergy

• fe = 0.9, consider adjusting dose if CrCl is reduced.

Severe penicillin allergy

Consult Infectious Diseases/Clinical Microbiology.

See Chronic Liver Disease on Hospital HealthPathways

Likely with an ascitic fluid white cell count of > 250 x10⁶/L with neutrophils predominant.

cefotaxime HMLNZFPMLnoids Cefotaxime F: n/a Half life: 1 hour Elimination: renal fe: 0.7

IV 2 g every eight hours

• fe = 0.7, consider adjusting dose if CrCl reduced.

Topic Code: 99236

must be prescribed or recommended by a consultant.