Canterbury DHB

Infected Ulcers (e.g. diabetic, vascular, pressure)

• Avoid IV/PO antimicrobials unless clear signs of active infection (use appropriate dressings)
• Often polymicrobial, and superficial swabs can be misleading/of limited value
• Consider underlying osteomyelitis, if probes to bone or underlying bony prominence
• If severe pain or systemically unwell, consider necrotising skin or soft tissue infection (fasciitis) and seek early ID/surgical involvement.

Pathogens

• Common: S. pyogenes, S. aureus, Enterobacteriaceae, anaerobes.

Drug Treatment

• Duration: Minimum of 10 days but longer is often required.

Empiric

Mild to moderate infection

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

IV 1 g/200 mg every eight hours then PO 500 mg/125 mg three times a day

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

Mild penicillin allergy

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

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

followed by

cefalexin HMLSchedNZFPML Cefalexin F: 0.9 Half life: 1 hour Elimination: renal fe: 0.9

PO 500 mg four times a day

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

AND

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

Severe penicillin allergy

ciprofloxacin HMLSchedNZFPMLnoids Ciprofloxacin F: 0.7 Half life: 4 hours Elimination: renal fe: 0.5 Additional points: Inhibits CYP1A2 and 3A. Antacids, milk, and enteral feeds ↓ absorption.

PO 500 mg twice a day

• Inhibits CYP1A2 (strong) and 3A.
• Subject to OAT and OATP (transporter) inhibition.
• Avoid in pregnancy and breastfeeding.

AND

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

PO 450 mg three times a day

• Metabolised by CYP3A. (fe < 0.1).

Severe infection

piperacillin+tazobactam HMLNZFPMLnoids Piperacillin+Tazobactam F: n/a Half life: 1 hour Elimination: renal fe: 0.8/0.6

IV 4 g/500 mg every eight hours

• If still on piperacillin+tazobactam beyond 48 hours, consider measuring a trough concentration. Consult Infectious Diseases for interpretation.
• fe (piperacillin) = 0.8, fe (tazobactam) = 0.6, consider adjusting dose if CrCl reduced.

Mild penicillin allergy

meropenem HMLNZFPMLnoids Meropenem F: n/a Half life: 1 hour Elimination: renal; hydrolysis fe: 0.7

IV 1 g every eight hours

• Meropenem rapidly and significantly reduces sodium valproate concentrations. Concomitant administration may precipitate seizures in patients with a pre-existing seizure disorder. Discuss alternative antibiotic options with Infectious Diseases/Clinical Microbiology.
• If still on meropenem beyond 48 hours, consider measuring a trough concentration. Consult Infectious Diseases for interpretation.
• fe = 0.7, start with full dose initially then consider extending dose interval and/or decreasing dose for subsequent doses if CrCl is reduced (< 30 mL/min). Consult pharmacist.

Severe penicillin allergy

Consult Infectious Diseases/Clinical Microbiology

must be prescribed or recommended by a consultant.

Topic Code: 99261