American Board of Internal Medicine (ABIM) Certification Practice Exam

The recommended oral dosage of Vancomycin for the first occurrence of non-fulminant Clostridioides difficile infection (CDI) is 125 mg administered four times daily for a duration of 10 days. This dosing regimen is established to effectively disrupt the growth of the C. difficile bacteria, which is critical for resolving the infection.

The rationale behind the dosing frequency is linked to achieving adequate drug levels in the gastrointestinal tract, where the infection occurs. Administering Vancomycin four times daily allows for better coverage and the possibility of reducing symptoms more effectively compared to less frequent dosing. Ensuring the antibiotic reaches sufficient concentrations can help in clearing the infection and prevent its recurrence.

For clarity on the other options, they would not meet the efficacy required for treating non-fulminant CDI appropriately. For instance, 125 mg twice daily is often considered insufficient to ensure therapeutic drug concentrations over a 10-day treatment period. Similarly, the three times daily regimen may also fail to provide the optimal therapeutic effect needed to resolve the infection. As for the 200 mg twice daily option, this dosage is not the standard for treating this type of CDI and does not align with current clinical guidelines, further underscoring the importance of adhering to