Empowering Pharmacists in Antimicrobial Stewardship: Enhancing Patient Care through Empirical, Prophylactic, and Definitive Therapy

 Antimicrobial Stewardship (AMS) refers to the optimal selection, dosing, and duration of antimicrobial treatment resulting in the best clinical outcome.

Pharmacists play a pivotal role in optimizing antimicrobial therapy across empirical, prophylactic, and definitive phases. Their expertise is essential for selecting appropriate agents, ensuring precise dosing, and mitigating the risks associated with antimicrobial resistance (AMR). Here’s an in-depth look at their contributions at each stage:

1.      Empirical Therapy

Empiric therapy is given to patients who have a proven or suspected infection, but the responsible organism(s) has or have not yet been identified.

Empirical therapy is initiated when there is a clinical indication of infection but before the pathogen is precisely identified. This approach relies on likely causative organisms based on infection site, patient history, and local resistance patterns.

However, before an empirical therapy is administered, samples from the suspected source of infection should have been drawn and sent to the laboratory for testing.

After appropriate clinical samples are taken, appropriately chosen antibiotic(s) should be given in a timely manner while balancing both the need for activity against the causative pathogens and the avoidance of unnecessary broad-spectrum coverage, which can potentially lead to antimicrobial resistance.

Pharmacist's Role in Empirical Therapy:

• Antimicrobial Selection: Pharmacists contribute to selecting an appropriate antimicrobial regimen, using knowledge of epidemiological data, probable pathogens, and patient factors such as comorbidities and allergy history.
• Dose Optimization: They determine optimal dosing and route of administration to achieve therapeutic concentrations quickly, especially critical in severe infections. Parameters like Liver function and Renal function have to be considered.
• Spectrum Management: Pharmacists advocate for the narrowest possible spectrum that will cover likely pathogens to avoid unnecessary selection pressure for resistance.
• Therapeutic Monitoring: Pharmacists monitor clinical indicators and biomarkers of infection to assess therapy efficacy, adjusting each treatment based on patient response or emerging diagnostic information.

2. Prophylactic Therapy

Prophylactic therapy aims to prevent infection in patients at high risk, such as surgical patients or those with immunosuppression. This preventive approach reduces the incidence of healthcare-associated infections (HAIs) by controlling exposure to potential pathogens. E.g. Surgical prophylaxis before surgical procedures.

Pharmacist's Role in Prophylactic Therapy:

• Risk Stratification: Identification of patients who meet criteria for antimicrobial prophylaxis based on the nature of the procedure or underlying immunological status.
• Selection of Agent and Dosage: They select antimicrobials with a spectrum specifically targeted to cover expected pathogens without excessive broad-spectrum coverage. Pharmacists also determine the appropriate dose to achieve effective tissue concentrations.
• Timing and Duration Control: Pharmacists ensure prophylactic agents are administered at the optimal time - commonly within 60 minutes before a surgical incision - and discontinued within 24 hours to reduce exposure, unless prolonged prophylaxis is justified. These guidelines can also be tailored to one’s area of practice.

In my current area of practice, prophylactic antibiotics must be administered in sufficient dosage 30 minutes prior to the incision (usually with induction of anaesthesia) to ensure adequate tissue concentration, and most certainly within two hours of the procedure. For procedures lasting greater than 3 hours, where there is rapid blood loss (over 1.5 litres) and/or fluid administration an additional dose of antibiotics is advised.

• Education and Surveillance: They educate the healthcare team on appropriate prophylactic protocols and monitor for any adverse reactions, adjusting treatment as necessary.

3. Definitive (Targeted) Therapy

Definitive therapy is initiated after pathogen identification and susceptibility testing. This phase allows precise targeting of the causative organism, typically reducing the need for broad-spectrum agents.

Once microbiology results have helped to identify the etiologic pathogen and/or antimicrobial susceptibility data are available, every attempt should be made to narrow the antibiotic spectrum.

Pharmacist's Role in Definitive Therapy:

• Pathogen-Specific Selection: Based on culture and sensitivity results, pharmacists de-escalate to a narrower-spectrum agent, aligning with stewardship goals to reduce AMR risks.
• Dose and Duration Adjustment: They tailor dosing regimens to match the pharmacokinetic and pharmacodynamic properties required to effectively eradicate the infection, minimizing toxicity and resistance risk.
• Ongoing Monitoring: Pharmacists provide continuous monitoring of patient response, observing for clinical improvement or signs of adverse effects. They may also facilitate therapeutic drug monitoring (TDM) for agents with narrow therapeutic indices for drugs such as Vancomycin and Amikacin.
• Patient Counselling: Pharmacists educate patients on the importance of adherence, potential side effects, and the rationale for therapy duration, enhancing compliance and therapeutic outcomes.

Overarching Contributions to Antimicrobial Stewardship

In all therapy stages, pharmacists are integral to antimicrobial stewardship (AMS) programs. They ensure rational antimicrobial use by carefully assessing each prescription’s necessity, duration, and potential impact on resistance. Their roles include supporting the formulation of institutional guidelines, conducting audits, and collaborating with interdisciplinary teams to implement best practices.

Pharmacists support the effectiveness of antimicrobials in individual cases and contribute to broader AMR containment efforts.