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Clonidine Overdose - Symptoms and Management

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Clonidine is a drug that is commonly used to treat high blood pressure. In this article, we discuss Clonidine and related imidazoline poisoning.

Written by

Dr. Sameeha M S

Medically reviewed by

Dr. Nagaraj

Published At November 15, 2022
Reviewed AtNovember 15, 2022


Untreated high blood pressure (hypertension) will cause damage to the blood vessels of the heart, brain, and kidneys. Later, it will result in heart failure, stroke, and kidney diseases. Clonidine is used for treating high blood pressure (hypertension) and is an imidazoline derivative. Imidazolines are derived from an organic compound, imidazole, by reducing a double bond. Imidazoline derivatives are used for nasal decongestion. Imidazoline derivative-containing medications (Clonidine) are mainly used for hypertension, drug withdrawal symptoms, diarrhea, menopausal flushing, attention deficit hyperactivity disorder, and spasticity. Clonidine overdose can cause adverse health conditions and need medical management.

What Is Clonidine?

Clonidine is an imidazoline derivative used to reduce blood pressure. It acts as an alpha-2 adrenergic agonist. Stimulation of alpha-2 receptors in the brain will cause suppression of sympathetic blood flow and thus reduces blood pressure. Clonidine will also act on imidazoline receptors in the brain (imidazoline -1) and contribute to reducing blood pressure. For attention-deficit hyperactivity disorder (ADHD) treatment, Clonidine acts by agonism (activates the receptor to produce a response) at the alpha-2A adrenergic receptor.

What Are the Uses of Clonidine?

  • Hypertension - Clonidine is highly effective for reducing high blood pressure by slowing the pulse rate. It reduces the serum concentration of renin, catecholamines, and aldosterone.

  • Attention Deficit Hyperactivity Disorder - Clonidine is used in attention deficit hyperactivity disorder patients to improve symptoms. Methylphenidate (central nervous system stimulant) and Clonidine are used for better response. Clonidine reduces sleep disturbances observed in attention deficit hyperactivity disorder (ADHD).

  • Spasticity - Clonidine can reduce muscle stiffness by inhibiting excessive sensory transmission to the area of muscle injury.

  • Drug Withdrawal - Clonidine can reduce the severity of drug withdrawal symptoms. It is commonly used for drug withdrawal symptoms related to nicotine, opioids, benzodiazepines, and alcohol. Sympathetic nervous system responses like excessive sweating, increased blood pressure, hot and cold flashes, and abnormal heart rate associated with opioid withdrawal are reduced after using Clonidine.

  • Dysmenorrhea - Severe painful menstrual cramps can be reduced by using Clonidine.

  • Tourette Syndrome - It is a neurodevelopmental syndrome associated with multiple motor movements and vocal tics. Clonidine helps to reduce the multiple movement reactions associated with Tourette syndrome.

What Are the Side Effects of Clonidine?

Certain side effects are observed in patients after Clonidine use. The common side effects associated are the following.

  • Nausea.

  • Headache.

  • Dry mouth.

  • Skin rashes.

  • Hoarseness of voice.

  • Vomiting.

  • Tiredness.

  • Hives.

  • Difficulty in breathing.

  • Malaise.

  • Hypotension.

  • Anxiety.

  • Erectile dysfunction.

  • Fever.

  • Irritability.

What Is Clonidine Poisoning?

Clonidine is a biochemical derivative of imidazoline. Clonidine poisoning may occur due to accidental ingestion by young children, suicidal ingestion, chronic use of large amounts of drugs, and transdermal exposure from a Clonidine patch. Due to this increased clinical use, accidental ingestion and misuse have increased in recent years. Clonidine is rapidly absorbed after oral ingestion. Peak blood concentration is observed two to four hours after ingestion. Many studies have shown that age-dependent and dose-dependent responses are observed in Clonidine poisoning. A high incidence of clinical effects associated with toxicity is seen in young children as compared to others. Clonidine overdose will cause toxicity and related changes in the body.

It includes the following.

  • Clonidine poisoning presents with symptoms like hypotension (low blood pressure), respiratory depression, somnolence (sleepiness), miosis (contraction of the pupil of the eye), and bradycardia (slow heart rate).

  • Initial symptoms like alteration in the level of consciousness will develop within one hour. It will later develop into cardiovascular effects within four hours after poisoning.

  • Hypothermia (very low body temperature) is also observed within a few hours after poisoning.

  • Cardiovascular and respiratory effects are observed with doses greater than 0.01 milligrams per kilogram to 0.2 milligrams per kilogram.

  • Respiratory depression associated with Clonidine poisoning is observed commonly in children. Respiratory failure may occur in individuals within a few hours after poisoning.

  • Central nervous system toxicity will cause lethargy (low energy) and slower neurological functions.

How Can We Manage Clonidine Poisoning?

Most of the symptoms associated with Clonidine overdose can be managed with medical intervention. Invasive intervention procedures are rare following Clonidine poisoning. Young children ingested with heavy doses of Clonidine may develop dangerous adverse effects and may need invasive interventions like intubation and vasopressors. After a Clonidine overdose, patients are observed for signs of toxicity. Within several hours of poisoning, toxic symptoms will develop. Supportive care and management are the basis of Clonidine overdose.

Management of Clonidine poisoning involves the following procedures:

  • Fluid Resuscitation - Hypotension (low blood pressure) is common after Clonidine toxicity. It can be managed by fluid resuscitation. Intravenous fluids and blood transfusions are done to manage hypotension.

  • Dopamine and Norepinephrine - Bradycardia (low heart rate) associated with Clonidine poisoning is treated using Dopamine and Norepinephrine. Dopamine is a peripheral vasostimulant and treats low blood pressure and heart rate.

  • Naloxone - It is administered to reverse respiratory depression, hypotension, bradycardia, and miosis associated with Clonidine overdose. Clonidine administration will trigger endogenous opioid release and also stimulate opioid receptors. Naloxone is an opioid receptor antagonist (opposes action) and will reverse these opioid effects. Naloxone doses ranging from 0.1 to 10 milligrams are used depending on the patient's condition.

  • Atropine - It is used to improve heart rate and reverse bradycardia induced by Clonidine poisoning.

  • Intubation - Adequate airway management is important in patients with acute respiratory distress after Clonidine poisoning. Severe respiratory depression is managed by endotracheal intubation.


Clonidine is a biochemical derivative of imidazoline used to treat hypertension,attention-deficit hyperactivity disorder (ADHD), sleep disturbances, drug withdrawal symptoms, and Tourette syndrome. Clonidine overdoses are common due to their wide use and availability. Accidental ingestion of Clonidine tablets by young children is very common, and care must be taken to avoid it. Early identification of poisoning, diagnosis, and medical management are essential to avoid dangerous health effects.

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Dr. Nagaraj
Dr. Nagaraj



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