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Principles of antimicrobial prescribing

Establish the need for antimicrobial therapy

A number of bacterial and viral diseases are self-limiting and do not benefit from antibiotics. Prescribing of antimicrobial therapy in such cases may expose the patient to undue risks and may contribute to the development of resistance.

Choose antimicrobials based on factors such as

  • Suspected / known infecting organism/s
  • Spectrum, safety profile and cost of available antimicrobials
  • Previous clinical experience
  • Potential for selection of resistant organisms
  • Risk of superinfection
  • Known drug allergy details
  • Interactions with other drugs

These factors should be considered in light of the clinical condition of the patient.

Prophylactic antimicrobial therapy should be restricted to situations where such therapy has been proven to be effective

The aim of prophylaxis in the surgical setting is to produce adequate tissue and plasma levels at the time contamination is most likely which is during the procedure.

Empirical antimicrobial therapy

Empirical antimicrobial therapy should be prescribed based on likely clinical diagnosis, suspected aetiology and local susceptibility test results. Where possible, such information has been incorporated into these guidelines. It is important, where possible, to:

  • Obtain a specimen BEFORE commencing antimicrobial therapy
  • Use the results of Gram stain or direct detection methods to prescribe specific therapy before culture results are available.

Directed antimicrobial therapy

Review of empirical antimicrobial prescribing should be made in light of available culture results. This information, considered in the context of the clinical condition of the patient, should be used to prescribe the most efficacious, cost-effective agent with the lowest incidence of toxicity and the narrowest spectrum of activity. Such practice will help to reduce the problems associated with broad-spectrum therapy i.e. selection of resistant microorganisms and superinfection.

Use oral therapy whenever safe and effective

Change from intravenous to oral therapy as soon as possible.

Further information

Last updated 16 November 2015
Last reviewed 16 November 2015