Summary: Clonidine is an alfa2-adrenergic receptor agonist that acts on the CNS to cause a reduction in the sympathetic response, leading to a decrease in peripheral and renovascular resistance, heart rate and blood pressure. For an oral regimen, the maximum plasma concentration is achieved in 3 to 4 hours and its physiological effects start 1 to 2 hours after administration and last for 8 hours. As a precaution, clonidine should be tapered slowly to avoid rebound hypertension. Side effects may include somnolence and dry mouth. Clonidine is mostly indicated as a treatment of hypertension. Recent studies gave new evidence, that clonidine and spironolactone treatment resulted (ReHOT) in similar BP control as fourth medical treatment for resistant hypertension patients and may be used in those with acute and severe hypertension.