Which medication can precipitate a hypertensive crisis if discontinued abruptly?

Clonidine is a centrally acting alpha-2 adrenergic agonist used primarily in the treatment of hypertension and attention deficit hyperactivity disorder. When clonidine is taken, it stimulates alpha-2 receptors in the brain, leading to decreased sympathetic outflow and reduced blood pressure. However, if clonidine is suddenly discontinued, there can be a rebound increase in sympathetic outflow, resulting in a significant rise in blood pressure, which can precipitate a hypertensive crisis.

This reaction occurs because the body, during the period of clonidine use, becomes reliant on the drug's effects to regulate sympathetic nervous system activity. The sudden withdrawal removes the inhibitory effects, leading to an exaggerated sympathetic response characterized by increased norepinephrine release, vasoconstriction, and consequently, an elevation in blood pressure.

In contrast, other medications listed do not have a similar profile regarding withdrawal. Diltiazem, a calcium channel blocker, does not typically cause rebound hypertension upon discontinuation. Valsartan, an angiotensin II receptor blocker, and hydrochlorothiazide, a thiazide diuretic, also do not precipitate hypertensive crises when stopped abruptly. While gradual tapering is generally a good practice for many medications, clonidine is particularly notable