Duration of Antibiotic Therapy: General Principles

Duration of Antibiotic Therapy: General Principles – Pharmacy Times – Maricelle O. Monteagudo-Chu, PharmD, BCPS-AQID, and Nageh Shaeishaa, RPH, MSC – July 2017

Deciding on the duration of antimicrobial therapy for an infection is neither straightforward nor simple. A short or long course of antibiotics can be given to a patient, depending on the drug used, the severity of an infection, and response to treatment (Table 1).

Original image is blurry too 

CHOICE OF AGENT

Antibiotics work by either selectively killing (bactericidal) or inhibiting the growth (bacteriostatic) of bacteria.

In most cases, more than 1 antibiotic is used to provide synergistic activity and rapid killing.

Another factor that can affect the efficacy of antibiotics is their ability to penetrate and remain (for an adequate time) at the site of infection.

TYPE AND SEVERITY OF INFECTION

A patient’s

  • immune status,
  • affected anatomical site, and
  • pathogen causing the infection

also should be considered when assessing duration of therapy.

Infected patients with no hemodynamic issues can be treated with short courses of antimicrobials.

The ability of antibiotics to penetrate necrotic tissues, abscesses, or biofilms also can limit their efficacy.

Infections can be difficult to treat and require prolonged antibiotic courses. Unless surgical intervention is undertaken to remove debris and/ or drain abscesses, antibiotics cannot reach infected sites.

ASSESSMENT OF PATIENT’S RESPONSE

Improvements in

  • hemodynamic status (eg, heart rate, blood pressure),
  • white blood cell count,
  • temperature,
  • oxygenation, and/or
  • radiologic findings

should be seen a few days after starting an effective therapy.

Once the signs and symptoms of infections are resolved, clinicians can consider terminating therapy.

Rechecking for cultures is not always necessary once a patient begins responding to therapy, except in the case of bloodstream infections.

The use of biomarkers, such as C-reactive protein (CRP), and the procalcitonin test also has been instrumental in evaluating antibiotic response and determining the duration of antibiotic therapy. Unlike CRP, procalcitonin is more specific to bacterial infections; therefore, the test has been used to curtail unnecessary antibiotic usage.

Use of the procalcitonin-guided algorithm has been shown to reduce the duration of exposure to antibiotics by ≤25% in patients with lower respiratory tract infections and 23% in patients who are critically ill.

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