What is a significant risk if central alpha-2 agonists like clonidine are discontinued abruptly?

When central alpha-2 agonists such as clonidine are discontinued abruptly, one of the most significant risks is the development of a hypertensive crisis. This occurs due to the sudden rebound activation of the sympathetic nervous system. Clonidine works by stimulating central alpha-2 adrenergic receptors, which decreases sympathetic outflow and lowers blood pressure. When the medication is stopped suddenly, there is a rapid increase in norepinephrine release, resulting in increased heart rate and blood pressure, which can lead to a hypertensive crisis. Symptoms may include severe headaches, dizziness, visual disturbances, and even complications like stroke if not managed promptly.

In contrast, while severe bradycardia, acute renal failure, and myocardial infarction are important clinical considerations in many contexts, they are not typical direct consequences of abruptly stopping clonidine therapy. Severe bradycardia could occur due to other factors or medications but is not a primary concern with the withdrawal of clonidine. Acute renal failure is more related to other medications or specific underlying conditions rather than the withdrawal of clonidine, and myocardial infarction risk is generally not directly associated with discontinuation but rather with underlying cardiovascular status and risk factors.