• Clonidine is a direct adrenergic agonist which is selective for alpha2 receptors. When given orally, clonidine lowers systemic arterial pressure. The precise mechanism by which clonidine exerts this anti-hypertensive effect is unknown; however, it is hypothesized that it is primarily due to action within the CNS rather than affecting peripheral autonomic fibers directly.
  • A major clinical disadvantage of clonidine and why it is infrequently used as a hypertensive is that when discontinued or when doses are missed, there is significant reflex hypertension.