Spasticity
Clonidine has some role in the treatment of spasticity, acting principally by inhibiting excessive sensory transmission below the level of injury. Its use, however, is mainly as a second or third line agent, due to side effects such as hypotension, bradycardia, and drowsiness. Other uses
Clonidine also has several off-label uses, and has been prescribed to treat psychiatric disorders including stress, sleep disorders,  hyperarousal caused by post-traumatic stress disorder, borderline personality disorder, and other anxiety disorders. Clonidine is also a mild sedative, and can be used as premedication before surgery or procedures. Its epidural use for pain during heart attack, and postoperative and intractable pain has also been studied extensively. Clonidine can be used in restless legs syndrome. It can also be used to treat facial flushing and redness associated with rosacea. It has also been successfully used topically in a clinical trial as a treatment for diabetic neuropathy. Clonidine can also be used for migraine headaches and hot flashes associated with menopause. Clonidine has also been used to treat refractory diarrhea associated with irritable bowel syndrome, fecal incontinence, diabetes, diarrhea associated with opioid withdrawal, intestinal failure, neuroendocrine tumors, and cholera. Clonidine can be used in the treatment of Tourette syndrome (specifically for tics).
Adverse effects
The principal adverse effects of clonidine are sedation, dry mouth, and hypotension (low blood pressure).By frequencyVery common (>10% frequency):

Common (1-10% frequency):

Uncommon (0.1-1% frequency):

Rare (<0.1% frequency):

Withdrawal
Because clonidine suppresses sympathetic outflow, resulting in lower blood pressure, sudden discontinuation can result in acute hypertension due to a rebound in sympathetic outflow. In extreme cases, this can result in a hypertensive crisis, which is a medical emergency.Clonidine therapy should generally be gradually tapered when discontinuing therapy to avoid rebound effects from occurring. Treatment of clonidine withdrawal hypertension depends on the severity of the condition. Reintroduction of clonidine for mild cases, alpha and beta blockers for more urgent situations. Beta blockers never should be used alone to treat clonidine withdrawal as alpha vasoconstriction would still continue. Pharmacology
Mechanism of action
Clonidine crosses the blood-brain barrier. High blood pressure
Clonidine treats high blood pressure by stimulating α2 receptors in the brainstem, which decreases peripheral vascular resistance, lowering blood pressure. It has specificity towards the presynaptic α2 receptors in the vasomotor center in the brainstem. This binding has a sympatholytic effect, suppresses release of norepinephrine, ATP, renin, and neuropeptide Y which if released would increase vascular resistance. : 201–203 Clonidine also acts as an agonist at imidazoline-1 (I1) receptors in the brain, and it is hypothesized that this effect may contribute to reducing blood pressure by reducing signaling in the sympathetic nervous system; this effect acts upstream of the central α2 agonist effect of clonidine. : 201–203 Clonidine may also cause bradycardia, theoretically by increasing signaling through the vagus nerve.