Kaplan USMLE Step 2: What caused 72-year-old’s withdrawal syndrome?

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

A 72-year-old man is brought to the emergency department because of heart palpitations and headache. His past medical history includes essential hypertension. He normally takes a variety of antihypertensive medications, but he ran out of "one or two of them" last night. His blood pressure is 210/120 mm Hg. Ophthalmoscopic examination shows arteriovenous nicking and papilledema. Urinalysis shows proteinuria. His systolic blood pressure readings in the past have not been greater than 175 mm Hg. The physician suspects that this patient's current condition is caused by the sudden withdrawal of a medication. Which of the following is the most likely medication?

A. Atenolol

B. Clonidine

C. Felodipine

D. Hydrochlorothiazide

E. Lisinopril

The correct answer is B.

Clonidine is a centrally acting alpha-adrenergic agonist that causes reduced sympathetic outflow from the central nervous system and can be used as a treatment-refractory anti-hypertensive agent. If stopped abruptly, clonidine can cause a withdrawal syndrome with severe rebound hypertension (choice B) and therefore needs to be tapered slowly.

Choice A. Beta-blockers such as atenolol can also cause a withdrawal syndrome if they are stopped abruptly due to increased sympathetic activity. There may be a rise in heart rate and blood pressure, but it is unlikely to cause profound rebound hypertension like clonidine.