Mechanism of Action
Clonidine is considered a centrally acting alpha-2 receptor agonist. When these receptors are stimulated, norepinephrine release is inhibited thus the heart rate decreases and there is a decrease in peripheral vascular resistance leading to decreased afterload and decreased systemic blood pressure.
Clonidine is considered a second line agent to treat hypertension and should not be used as initial therapy or by itself. The FDA approved indications for clonidine is in the treatment of hypertension, severe cancer-related pain (given epidurally) and for attention deficit hyperactivity disorder (ADHD).
There are multiple other uses for clonidine including opioid, nicotine or alcohol withdrawal, anxiety, night sweats, insomnia and menopausal symptoms.
Dry mouth, dizziness, constipation, fatigue, bradycardia.
Rebound hypertension occurs upon clonidine withdrawal and thus it should be weaned off slowly. Giving a beta-blocker with alpha blocking properties such as carvedilol or labetalol can be helpful. Pure beta-blockers should be avoided since this can lead to unopposed alpha agonism, hypertension and arterial vasospasm.
Clonidine can be given as a transdermal patch.