Clonidine lowers blood pressure by decreasing the levels of certain chemicals in your blood. This allows your blood vessels to relax and your heart to beat more slowly and easily.
The Catapres brand of clonidine is used to treat hypertension (high blood pressure). The Kapvay brand is used to treat attention deficit hyperactivity disorder (ADHD).
Clonidine is sometimes given with other medications.
Take clonidine exactly as it was prescribed for you. Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not take this medicine in larger or smaller amounts or for longer than recommended.
Clonidine is usually taken in the morning and at bedtime. If you take different doses of this medicine at each dosing time, it may be best to take the larger dose at bedtime.
Clonidine may be taken with or without food.
Do not use two forms of clonidine at the same time. This medicine is also available as a transdermal patch worn on the skin.
Do not crush, chew, or break an extended-release tablet. Swallow it whole. Tell your doctor if you have trouble swallowing the tablet.
If you need surgery, tell the surgeon ahead of time that you are using clonidine. You may need to stop using the medicine for a short time.
Do not stop using clonidine suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.
Call your doctor if you are sick with vomiting. Prolonged illness can make it harder for your body to absorb this medicine, which may lead to withdrawal symptoms. This is especially important for a child taking clonidine.
If you are being treated for high blood pressure, keep using this medication even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.
if you have signs of an allergic reaction to clonidine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
severe chest pain, shortness of breath, irregular heartbeats;
a very slow heart rate;
severe headache, pounding in your neck or ears, blurred vision;
anxiety, confusion; or
a light-headed feeling, like you might pass out.
Serious side effects may be more likely in older adults.
Common clonidine side effects may include:
feeling tired or irritable;
dry mouth, loss of appetite;
dry eyes, contact lens discomfort; or
sleep problems (insomnia), nightmares.
This is not a complete list of side effects and others may occur.
Keep at room temperature away from light and moisture
Clonidine may potentiate the CNS-depressive effects of alcohol, barbiturates or other sedating drugs. If a patient receiving clonidine hydrochloride is also taking tricyclic antidepressants, the hypotensive effect of clonidine may be reduced, necessitating an increase in the clonidine dose. If a patient receiving clonidine is also taking neuroleptics, orthostatic regulation disturbances (e.g., orthostatic hypotension, dizziness, fatigue) may be induced or exacerbated.
Monitor heart rate in patients receiving clonidine concomitantly with agents known to affect sinus node function or AV nodal conduction, e.g., digitalis, calcium channel blockers and beta-blockers. Sinus bradycardia resulting in hospitalization and pacemaker insertion has been reported in association with the use of clonidine concomitantly with diltiazem or verapamil.
Amitriptyline in combination with clonidine enhances the manifestation of corneal lesions in rats (see Toxicology).
Based on observations in patients in a state of alcoholic delirium it has been suggested that high intravenous doses of clonidine may increase the arrhythmogenic potential (QTprolongation, ventricular fibrillation) of high intravenous doses of haloperidol. Causal relationship and relevance for clonidine oral tablets have not been established.
Hypertension may develop early and may be followed by hypotension, bradycardia, respiratory depression, hypothermia, drowsiness, decreased or absent reflexes, weakness, irritability and miosis. The frequency of CNS depression may be higher in children than adults. Large overdoses may result in reversible cardiac conduction defects or dysrhythmias, apnea, coma and seizures. Signs and symptoms of overdose generally occur within 30 minutes to two hours after exposure. As little as 0.1 mg of clonidine has produced signs of toxicity in children.
There is no specific antidote for clonidine overdosage. Clonidine overdosage may result in the rapid development of CNS depression; therefore, induction of vomiting with ipecac syrup is not recommended. Gastric lavage may be indicated following recent and/or large ingestions. Administration of activated charcoal and/or a cathartic may be beneficial. Supportive care may include atropine sulfate for bradycardia, intravenous fluids and/or vasopressor agents for hypotension and vasodilators for hypertension. Naloxone may be a useful adjunct for the management of clonidine-induced respiratory depression, hypotension and/or coma; blood pressure should be monitored since the administration of naloxone has occasionally resulted in paradoxical hypertension. Dialysis is not likely to significantly enhance the elimination of clonidine.
The largest overdose reported to date involved a 28-year old male who ingested 100 mg of clonidine hydrochloride powder. This patient developed hypertension followed by hypotension, bradycardia, apnea, hallucinations, semicoma, and premature ventricular contractions. The patient fully recovered after intensive treatment. Plasma clonidine levels were 60 ng/ml after 1 hour, 190 ng/ml after 1.5 hours, 370 ng/ml after 2 hours, and 120 ng/ml after 5.5 and 6.5 hours. In mice and rats, the oral LD50 of clonidine is 206 and 465 mg/kg, respectively