An overweight 55-year-old female visits the ambulatory care clinic for a scheduled blood p… — USMLE Step 3

An overweight 55-year-old female visits the ambulatory care clinic for a scheduled blood pressure check. Two weeks ago, she was diagnosed with primary hypertension and prescribed daily oral losartan. Her baseline serum creatinine was $0.9 \text{ mg/dL}$ and serum potassium was $4.2 \text{ mEq/L}$ . Today, she feels well and denies any dizziness, headache, or edema. Her blood pressure is $128/78 \text{ mmHg}$ . Repeat laboratory testing shows a serum creatinine of $1.1 \text{ mg/dL}$ and a serum potassium of $4.6 \text{ mEq/L}$ . Which of the following are the most appropriate next steps in monitoring and treatment evaluation? (Select two)

Continue the current dose of losartanAnswer
Schedule a routine clinical follow-up in 4 weeksAnswer
C
Discontinue the losartan and switch to a calcium channel blocker
D
Order a renal artery duplex ultrasound
E
Add spironolactone to optimize blood pressure control

Answer

Continue the current dose of losartan AND schedule a routine clinical follow-up in 4 weeks.

Angiotensin II receptor blockers (ARBs) such as losartan exert their antihypertensive effect partly by dilating the efferent arteriole in the kidney. This decreases intraglomerular pressure, which commonly leads to a benign, expected rise in serum creatinine of up to 30% from baseline. In this patient, the creatinine increased from

0.9 \text{ mg/dL}

1.1 \text{ mg/dL}

, an increase of approximately 22%, which is well within the acceptable physiologic threshold. Furthermore, her serum potassium remains safely within normal limits (

4.6 \text{ mEq/L}

), and her blood pressure has reached an excellent therapeutic target (

128/78 \text{ mmHg}

). Therefore, the most appropriate management is to continue the current effective medication regimen without any dose adjustments and schedule a routine follow-up appointment in approximately 4 weeks to ensure continued stability.

Step-by-Step Solution

Evaluate the patient's clinical and hemodynamic response to the prescribed losartan.

The patient is asymptomatic and her blood pressure is well-controlled at

128/78 \text{ mmHg}

Determines if antihypertensive efficacy has been achieved.

Analyze the follow-up basic metabolic panel for potential adverse medication effects.

Creatinine increased by approximately 22% (from

0.9 \text{ mg/dL}

1.1 \text{ mg/dL}

) and potassium increased slightly to

4.6 \text{ mEq/L}

Angiotensin II receptor blockers (ARBs) can cause hyperkalemia and functional changes in the kidneys.

Determine the clinical significance of the observed laboratory changes.

The changes are within acceptable and safe limits. A serum creatinine increase of up to 30% from baseline is an expected physiologic response.

Misinterpreting this expected benign change could lead to inappropriate discontinuation of a highly effective medication.

Key Concept

Expected physiologic laboratory changes during ACE inhibitor or ARB initiation.

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