Clonidine hydrochloride

Clonidine hydrochloride (Catapres) is a direct-acting α2 adrenergic agonist with an ED50 of 0.02±0.01 mg/kg. It treats high blood pressure by stimulating α2 receptors in the brain, which decreases cardiac output and peripheral vascular resistance, lowering blood pressure. It has specificity towards the presynaptic α2 receptors in the vasomotor center in the brainstem. This binding decreases presynaptic calcium levels, and inhibits the release of norepinephrine (NE). The net effect is a decrease in sympathetic tone.