American Board of Internal Medicine (ABIM) Certification Practice Exam

When undergoing outpatient parenteral antimicrobial therapy with nafcillin, which parameter must be monitored weekly?

1. Patient's blood pressure

2. Serum creatinine level

3. Liver biopsy results

4. Electrolyte levels

The correct answer is: Serum creatinine level

When a patient is undergoing outpatient parenteral antimicrobial therapy with nafcillin, it's crucial to monitor the serum creatinine level on a weekly basis. Nafcillin, a penicillin antibiotic, is primarily eliminated through the kidneys. As such, renal function can be significantly impacted during treatment, particularly in patients who may have pre-existing kidney issues or other risk factors for renal impairment. Monitoring serum creatinine helps healthcare providers identify any changes in kidney function early, allowing for prompt adjustments to medication dosing or the overall treatment regimen if required. It is particularly important because elevated creatinine levels can indicate impaired renal clearance of nafcillin, which could lead to increased risk of toxicity or adverse effects. In contrast, while monitoring blood pressure, liver biopsy results, and electrolyte levels may be relevant in certain clinical scenarios, they are not specifically necessary for the management of nafcillin therapy in an outpatient setting. Thus, focusing on serum creatinine is critical to ensure the safety and efficacy of the treatment.