CDHB Antimicrobial Guidelines

The South Canterbury, Taranaki, and West Coast DHBs endorse the Canterbury DHB Pink Book Antimicrobial Guidelines.

These guidelines are for use in ADULT patients only.

Information contained in these guidelines is provided to assist with medicine therapy and should be used in conjunction with pertinent clinical data. Final responsibility for drug use rests with the prescriber.

• Many antimicrobials have PHARMAC restrictions for hospital use in place. The restrictions usually:
  • apply to antimicrobials that are broad-spectrum, have specialised indications, are used to treat multi-drug resistant organisms, or have significant toxicity.
  • align with antimicrobial stewardship – optimising treatment of infections, while minimising antimicrobial resistance and toxicity.
  • require patient-specific Infectious Diseases/Clinical Microbiology approval, or compliance with CDHB Infectious Diseases agreed antimicrobial guidelines (e.g. Pink Book). See www.pharmac.health.nz, or consult your ward pharmacist or drug information ( 80900) for further information.
• Document in the clinical notes which criteria, recommendation, or guideline applies.

These guidelines are usually reviewed every two years using relevant international guidelines and consensus documents, and local susceptibility data and expert opinion.

Penicillin Allergy

See Adverse Reactions to Penicillins in Adults on Hospital HealthPathways.

Intravenous Antimicrobial Therapy

Patients should be started on intravenous (IV) antimicrobials if they fulfil any of these indications:

• Sepsis – clinical symptoms of infection (fever, sweats, chills or rigors) and at least 2 of the following criteria:
  • Temperature > 38ºC or < 36ºC
  • Tachycardia > 90 beats per minute
  • Tachypnoea > 20 breaths per minute
  • WBC count >12 or < 4x10⁹/L or the presence of immature neutrophils (toxic granulation).
• Severe sepsis – hypoperfusion, hypotension, organ dysfunction.
• Febrile neutropenia or immunosuppression.
• Community acquired pneumonia (CURB score ≥ 3).
• Other specific indications e.g. endocarditis, meningitis, septic arthritis, osteomyelitis, or some abscesses.
• Oral route compromised.
• Post surgical and unable to tolerate fluids.
• No oral formulation available.

Some antimicrobials have high oral availability and are tolerated at high oral doses.

General Antimicrobial Advice

• Obtain a recent hospitalisation and travel history.
• Identify allergies (see penicillin allergy).
• Check results for recent cultures and susceptibilities. Local antibiograms are found here:
  • Canterbury Health Laboratories antibiogram
  • Southern Community Laboratories antibiogram
• Identify any organisms of particular concern, e.g. methicillin-resistant Staphylococcus aureus (MRSA), extended spectrum beta-lactamase (ESBL) producers, vancomycin resistant enterococci (VRE). Recent overseas travel may be a risk factor for these.
• Give antimicrobial treatment based on these antimicrobial guidelines and recent susceptibility results.
• After susceptibility testing, use the narrowest spectrum antimicrobial to treat the infection.
• Identify any patient factors or drugs that might affect antimicrobial treatment, e.g. renal dysfunction, warfarin therapy.
• Contact Infectious Diseases or Clinical Microbiology with any concerns or for advice.

Intravenous (IV) to Oral (PO) Switch

• Patients should be switched to oral therapy as soon as possible. Most IV antimicrobials can be switched to oral within 2 to 3 days.
• All IV antimicrobials should be reviewed within 48 hours and on a daily basis thereafter.
• Studies comparing early switch to oral treatment demonstrate equal efficacy to continued IV therapy.
• Switch to oral therapy if patient no longer meets any of the criteria for IV treatment and they are improving clinically.
• Prolonged use of IV antimicrobials is associated with complications arising from the route of administration and increased cost.

Antimicrobial Intravenous to Oral Switch Protocol

* these drugs have very high oral availability

Antimicrobial Susceptibilities

Local antimicrobial susceptibility patterns (also known as “antimicrobial sensitivities” or “antibiogram”) are found here:

• Canterbury Health Laboratories antibiogram
• Southern Community Laboratories antibiogram

Probenecid

• Probenecid is sometimes prescribed with beta-lactams such as flucloxacillin and cefazolin to reduce the need for intravenous antimicrobial therapy and to allow less frequent oral dosing.
• Probenecid should not be used if eGFR is < 30 mL/min (see prescribing in renal impairment).
• For flucloxacillin:
  • Probenecid approximately doubles flucloxacillin concentrations, which may enable an earlier IV to PO switch, and less frequent oral dosing on discharge – i.e. three times daily instead of four times daily dosing.
  • Probenecid should not be prescribed to increase ("boost") beta-lactam concentrations for inpatients receiving flucloxacillin (or cefazolin) IV. It is better to prescribe adequate doses of the beta-lactam IV alone, rather than complicate treatment by adding probenecid.
  • When prescribing probenecid with flucloxacillin, give both agents orally at the same dose time (usually three times daily) and with food.
  • If unclear about antibiotic choice or dose, consult Infectious Diseases.
• For cefazolin:
  • Do not prescribe probenecid to increase cefazolin concentrations for inpatients – prescribe adequate doses of cefazolin alone.

Probenecid has many drug interactions – check for these before prescribing
(see Clinical Pharmacology bulletin November 2022 on the Christchurch Medicines Information Service).

• May be metabolised by glucuronidation. (fe = 0.1).
• Inhibits OAT and OATP (transporter).
• Decreases clearance of many renally cleared drugs (e.g. methotrexate, cefazolin).
• Efficacy of probenecid declines as renal function declines and is generally ineffective with CrCl < 30 mL/min.
• Can precipitate or aggravate gout. Do not initiate during an acute attack.

Topic Code: 90640

must be prescribed or recommended by a consultant.