Principles of Good Prescribing

Principles of antimicrobial therapy provide a framework that allows clinicians to optimise outcomes in patients with infections.

In general, the use of antimicrobials can be Prophylactic, Preemptive, Empiric or Definitive.

• Prophylactically to prevent infection, e.g. infective endocarditis, surgical prophylaxis

• Preemptively to abort infection, e.g. CMV infection in transplant recipients

• Empirically to provide initial control of infection in the absence of knowledge of its etiology, e.g. sepsis

• Definitively to cure an infection of known etiology

The importance of the choice of an appropriate empiric antibiotic regimen in patients with severe infections is evidenced by the fact that inappropriate therapy is associated with increased mortality. Furthermore, the antibiotic must be administered as rapidly as possible, preferably within one hour.

Ten important elements in the choice of antibiotics for empiric use:

1) Assess the infection

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2) Obtain cultures before the initiation of antibiotic therapy without delay in antibiotic administration

3) Document indication for antibiotics

4) Control the source e.g. drainage of an abscess or removal of a central venous access device

5) Reassess the need and the choice of selected antibiotic after 48 to 72 hours once microbiological information is available and the patient’s clinical status has evolved

6) De-escalate once susceptibilities are available to the narrowest spectrum to prevent the development of resistance, reduce toxicity and costs

7) Avoid double coverage with antibiotics, except in certain immunocompromised conditions

8) Monitor side effects and therapeutic drug levels (if applicable)

9) Consider IV to oral conversion once criteria are met

10) Shorten the duration of therapy based on the best evidence available

If cultures are negative, decision-making is often more complex and an assessment should be made of the patient’s clinical condition. In this instance, depending on clinical status and other available information such as serum procalcitonin measurements, the five ‘antimicrobial prescribing decision’ options are Stop, Switch, Change, Continue and OPAT.

• Stop antibiotics if there is no evidence of infection
• Switch antibiotics from IV to oral
• Change antibiotics – ideally to a narrower spectrum – or broader if required. Prescribers should seek expert advice when necessary
• Continue and document the next review date or stop date for IV and oral antibiotics
• Outpatient Parenteral Antibiotic Therapy (OPAT)

Patients on antibiotics should receive the right drug, at the right dose, at the right time and the right duration.

Promote good infection prevention and control measures to reduce cross-infection; proactively reducing the number of infections can, in turn, reduce the frequency of antibiotic prescriptions and have a positive impact on reducing antibiotic resistance – ‘Start Smart then Focus’.

Primary care prescribers should only prescribe antibiotics when they are needed for bacterial infections, and not for self-limiting mild infections such as colds, most coughs, sinusitis, earache and sore throats. Studies show that patients are less likely to ask their doctors for antibiotics if advised what to expect in the course of an illness and given a self-care plan. Delayed prescriptions when appropriate can be given.

BSAC have FutureLearn courses on OPAT and IVOST, to further enhance your understanding of these topics.

In the comments below, please discuss the following:

• Do you have an easily accessible antibiotic guideline in place to help the prescribing decision for patients in your organisation?
• Think of how you might monitor adherence to any guidance where you work.