Pharmacy PEBC Practice Exam

PB is a 70 year old female who is on the final day of a 10-day course of cotrimoxazole DS, i po bid for mild pyelonephritis. PB’s medical conditions include hypertension and osteoarthritis, for which she takes enalapril 5 mg po bid and acetaminophen 650 mg po qid. PB has been feeling unwell for the past two days, complaining of abdominal pain, diarrhea, and muscle weakness. She presents to the emergency department, where it is discovered that her serum potassium level is 5.9 mmol/L (normal: 3.5-5.0 mmol/L) and her estimated creatinine clearance is 70 mL/min. One month later, PB returns to her family physician with symptoms of another urinary tract infection (UTI). When hospitalized last month, her urinalysis showed resolution of the original UTI. This is now PB’s third UTI in the past six months. She is still taking enalapril and acetaminophen as before, and she has no known allergies. After resolution of the current infection, which of the following is the most appropriate regimen for UTI prophylaxis for PB?

1. Cotrimoxazole

2. Trimethoprim

3. Nitrofurantoin

4. Prophylaxis is not indicated for PB.

The correct answer is: Nitrofurantoin

Explanation PB's recent potassium level and creatinine clearance indicate that she may be at risk of developing kidney problems. Both cotrimoxazole and trimethoprim may further increase her potassium levels, leading to serious health complications. Thus, these options are not recommended to be used as prophylaxis for UTI. Additionally, PB's frequent and recurrent UTIs suggest that she may benefit from a longer-term prophylaxis, making nitrofurantoin a more appropriate choice compared to a short-term use of cotrimoxazole. Finally, prophylaxis is indicated for PB as she has experienced three UTIs in the past six months. Therefore, the most appropriate option for PB is nitrofurantoin for UTI prophylaxis.