Indications
Clonidine Hydrochloride is used to treat high blood pressure (hypertension). Extended-release (ER) tablets are also used, alone or with stimulant medicines, for attention deficit hyperactivity disorder (ADHD). Doctors sometimes use it for other conditions, such as reducing withdrawal symptoms from opioids or for menopausal hot flushes, and low doses are used to prevent migraine in some countries.
How It Works
Clonidine acts on alpha-2 receptors in the brain. This reduces the nerve signals that tighten blood vessels and speed up the heart, so blood vessels relax, the heart rate slows a little and blood pressure falls. In ADHD, its action in the front part of the brain is thought to help with attention and impulse control.
Dosage and Administration
For high blood pressure in adults, a usual starting dose is 0.1 mg twice a day (morning and bedtime), which the doctor increases slowly until blood pressure is controlled. A larger share of the dose may be given at bedtime to reduce daytime sleepiness. For ADHD, extended-release tablets are used only as prescribed and must be swallowed whole. Doses for children and for other uses are set by the doctor. Never stop clonidine suddenly; the dose must be reduced gradually over several days.
Interactions
Alcohol, sleeping pills, sedating antihistamines, strong painkillers and other medicines that cause drowsiness add to its sedating effect. Other blood pressure medicines increase the fall in blood pressure. Beta blockers such as Propranolol, Digoxin, Verapamil and Diltiazem can slow the heart too much, and beta blockers can worsen the rebound rise in blood pressure if clonidine is stopped. Tricyclic antidepressants and Mirtazapine may reduce its effect.
Contraindications
Do not use clonidine if you are allergic to it, or if you have a very slow heartbeat caused by certain heart rhythm problems (such as sick sinus syndrome or second or third degree heart block) and do not have a pacemaker.
Side Effects
Common side effects include drowsiness, tiredness, dry mouth, dizziness especially on standing, constipation, headache and low mood. Less common effects include a slow heartbeat, sleep problems, nightmares, sexual problems and dry eyes.
Get urgent medical help if you faint, have a very slow or irregular heartbeat, severe dizziness, chest pain, or signs of a serious allergic reaction. If doses are missed or stopped suddenly, a dangerous rise in blood pressure with headache, agitation, sweating and a fast heartbeat can occur and needs urgent care.
Pregnancy and Lactation
Clonidine is used in pregnancy only if the doctor feels it is needed. It passes into breast milk and may make the baby drowsy or lower its blood pressure, so it is generally not recommended while breastfeeding. Discuss with your doctor.
Precautions and Warnings
Take doses regularly and do not run out of tablets. Use with care in heart disease, recent heart attack, stroke, kidney disease, depression, and in older people. Stand up slowly to avoid dizziness. It can make you sleepy, so do not drive or use machines until you know how it affects you, and avoid alcohol. Tell your surgeon or anaesthetist that you take clonidine.
Overdose
Overdose can cause severe drowsiness, slow breathing, a very slow heartbeat, low blood pressure, small pupils and low body temperature. Children are very sensitive even to one tablet. Get emergency medical help straight away.
Therapeutic Class
Centrally acting antihypertensive, alpha-2 adrenergic agonist.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.