Clonidine Side Effects

Brand Names: Catapres, Duraclon

Please note - some side effects for Clonidine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Clonidine - for the Consumer

Clonidine

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Clonidine:

Chest pain; confusion; constipation; drowsiness; dry mouth; flushing; general weakness; headache; nausea; ringing in the ears; sweating; tiredness; vomiting.

Severe allergic reactions (rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; decreased heartbeat; dizziness; fainting; fever; hallucinations; lightheadedness; painful burning on urination.

Clonidine Patches

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Clonidine Patches:

Dizziness; drowsiness; dry mouth or throat; headache; lack of energy; mild skin irritation; tiredness; trouble sleeping.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; decrease sexual desire or ability; fainting; fast, slow, or irregular heartbeat; hallucinations; mental or mood changes; severe or persistent headache or dizziness; skin irritation; rash, blisters, burning, or color change at the application site; swelling of the hands, ankles, or feet.

Clonidine Tablets

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Clonidine Tablets:

Constipation; dizziness; drowsiness; dry mouth; nausea; tiredness; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; decreased sexual desire or ability; fainting; fast, slow, or irregular heartbeat; hallucinations; mental or mood changes; severe or persistent headache or dizziness; swelling of the hands, ankles, or feet.

Clonidine Side Effects - for the Professional

Clonidine

Most adverse effects are mild and tend to diminish with continued therapy. The most frequent (which appear to be dose-related) are dry mouth, occurring in about 40 of 100 patients; drowsiness, about 33 in 100; dizziness, about 16 in 100; constipation and sedation, each about 10 in 100.

The following less frequent adverse experiences have also been reported in patients receiving Clonidine hydrochloride USP, but in many cases patients were receiving concomitant medication and a causal relationship has not been established.

Body as a Whole

Weakness, about 10 in 100 patients; fatigue, about 4 in 100; headache and withdrawal syndrome each about 1 in 100. Also reported were pallor; a weakly positive Coombs' test; increased sensitivity to alcohol; and fever.

Cardiovascular

Orthostatic symptoms, about 3 in 100 patients; palpitations and tachycardia, and bradycardia, each about 5 in 1000. Syncope, Raynaud's phenomenon, congestive heart failure, and electrocardiographic abnormalities (i.e., sinus node arrest, junctional bradycardia, high degree AV block and arrhythmias) have been reported rarely. Rare cases of sinus bradycardia and atrioventricular block have been reported, both with and without the use of concomitant digitalis.

Central Nervous System

Nervousness and agitation, about 3 in 100 patients; mental depression, about 1 in 100 and insomnia, about 5 in 1000. Other behavioral changes, vivid dreams or nightmares, restlessness, anxiety, visual and auditory hallucinations and delirium have rarely been reported.

Dermatological

Rash, about 1 in 100 patients; pruritus, about 7 in 1000; hives, angioneurotic edema and urticaria, about 5 in 1000; alopecia, about 2 in 1000.

Gastrointestinal

Nausea and vomiting, about 5 in 100 patients; anorexia and malaise, each about 1 in 100; mild transient abnormalities in liver function tests, about 1 in 100; hepatitis, parotitis, constipation, pseudo-obstruction, and abdominal pain, rarely.

Genitourinary

Decreased sexual activity, impotence and loss of libido, about 3 in 100 patients; nocturia, about 1 in 100; difficulty in micturition, about 2 in 1000; urinary retention, about 1 in 1000.

Hematologic

Thrombocytopenia, rarely.

Metabolic

Weight gain, about 1 in 100 patients; gynecomastia, about 1 in 1000; transient elevation of blood glucose or serum creatine phosphokinase, rarely.

Musculoskeletal

Muscle or joint pain, about 6 in 1000 and leg cramps, about 3 in 1000.

Oro-otolaryngeal

Dryness of the nasal mucosa was rarely reported.

Ophthalmological

Dryness of the eyes, burning of the eyes and blurred vision were reported.

Side Effects by Body System

Other

The most common adverse side effects are related to the alpha-adrenergic blocking effects of clonidine. These side effects are dose-related, typically decrease over time, and mostly affect the nervous system, cardiovascular system, and the gastrointestinal system.

Nervous system

Nervous system side effects have included drowsiness (28%), dizziness (9%). Patients with decreased autoregulation of cerebral blood flow appear to be at increased risk for clonidine-induced cerebral hypoperfusion if blood pressure is lowered too much or too quickly. This may be important in some elderly patients. Confusion (13.2%) and hallucinations (5.3%) have been reported with epidural usage. Dose-dependent sedative effects, memory impairment, and reduced cognitive performance have been reported in subjects receiving intravenous clonidine.

A study of 13 patients who had pre- and post-clonidine cerebral blood flow (CBF) measured by nuclear scanning revealed that patients with a initially high pretreatment CBF tended to demonstrate decreased CBF after clonidine therapy.

Patients with traumatic spinal cord injury receiving clonidine may experience a delayed-onset of sedation regardless of the route of administration (i.e., intrathecal, intramuscular).

Cardiovascular

Cardiovascular side effects have included hypotension and sinus and atrioventricular arrhythmias. Postural hypotension occurs in 2% of patients. Rebound hypertension (which may be worse than pretreatment values) can present as irritability, tremors, headache, increased salivation, nausea, and palpitations. Rebound hypertension may be minimized by gradual reduction of dosage over two to four days.

Hypotension with epidural clonidine has been reported in 45% of 38 patients in one study. Hypotension occurred more commonly in the first four days, in women, in lower weight patients, and those receiving higher dosages.

Other cardiovascular side effects have included sinus bradycardia in approximately 0.3% of patients. A rare case of sinus arrest associated with clonidine has been reported. Patients with preexisting sinus node dysfunction, patients who have developed bradycardia while taking other sympatholytic agents, patients who are on another sympatholytic agent, and patients with renal dysfunction are at increased risk of clonidine-associated sinus bradycardia. Clonidine may cause hypertension in some patients with idiopathic orthostatic hypotension, particularly those with autonomic nervous system dysfunction.

A case of sinus arrest associated with clonidine has been reported. A 65-year-old man with diabetes, hypertension and unexplained syncope developed more frequent syncope and dizziness associated with documented episodes of sinus arrest during the first week of clonidine therapy. The patient had no hypoglycemia or orthostatic changes. The syncope and dizziness resolved upon discontinuation of clonidine; continuous electrocardiographic monitoring revealed a gradual and complete disappearance of sinus pauses. Junctional bradycardia and AV heart block have also been reported.

Ventricular tachycardia (VT) relatively refractory to lidocaine, but responsive to intravenous phentolamine, has been associated with clonidine withdrawal (case report). The authors believe that the VT was probably produced by humoral or neural stimulation of unregulated myocardial alpha-adrenergic receptors.

Transdermal clonidine has been implicated with hypertension in a quadriplegic patient with a C4 spinal lesion. The proposed mechanism is predominance of clonidine's peripheral alpha-1 adrenergic effects due to the patient's autonomic dysfunction, resulting in vasoconstriction and hypertension.

Sinus bradycardia or other supraventricular bradyarrhythmias are more likely in patients with underlying renal dysfunction.

In one case report, severe hypotension occurred during separation from cardiopulmonary bypass in a patient given intrathecal clonidine. The patient responded to volume expansion and use of vasoconstrictors.

Gastrointestinal

Gastrointestinal side effects have most commonly included dry mouth (30%) and constipation (15%). Nausea (13.2%) and vomiting (10.5%) have been reported with epidural clonidine.

Genitourinary

Genitourinary side effects have included impotence in male patients (24%), retrograde and delayed ejaculation, and an inability to achieve orgasm in female patients.

Dermatologic

Dermatologic reactions have been reported in 10% to 38% of patients who use transdermal clonidine. These reactions include psoriasis exacerbations and local dermatitis and/or pigmentation.

A 66-year-old woman with a history of psoriasis in remission developed erythematous, scaly plaques on the extensor surfaces of her forearms within three days after beginning clonidine therapy for control of flushing. The author of this case report suspected that clonidine may cause a fall in intracellular cAMP, leading to epidermal cell proliferation, and, in some cases, a psoriasiform eruption.

Psychiatric

Psychiatric side effects have included rare reports of depression, which has been the most common psychiatric reaction to clonidine. Rare cases of frank psychoses and delirium have been associated with clonidine withdrawal.

Endocrine

Endocrinologic side effects have been limited to rare cases of gynecomastia, hyperprolactinemia, or hyperglycemia.

A 68-year-old black man with hypertension, status post unilateral nephrectomy, was incidentally found to have 4+ proteinuria, 1+ glycosuria, new elevated blood glucose levels, and between 1.8 and 5.4 grams of protein per 24-hour urine collection within 6 weeks after starting clonidine. The signs and symptoms of diabetes and the nephrotic syndrome disappeared within five months after discontinuation of clonidine. Because of his solitary kidney, a renal biopsy was not performed.

Musculoskeletal

Musculoskeletal side effects have been rare. Moderately severe myalgia has been associated with the use of clonidine in patients treated for opioid withdrawal symptoms.

Immunologic

A 46-year-old woman developed forearm edema, mild thenar atrophy, and skin hypopigmentation within three months after beginning clonidine for perimenopausal flushing. Electromyelography was consistent with carpal tunnel syndrome. At surgical decompression, a skin biopsy revealed changes consistent with immune-complex disease. The patient's signs and symptoms abated after physical therapy and discontinuation of clonidine.

Immunologic side effects have rarely been reported and include one case of immune-complex disease.

Respiratory

Respiratory system reactions have been extremely rare. A case of severe bronchospasm associated with clonidine has been reported in the pediatric literature.

A 9-year-old boy with asthma developed a severe asthma attack after an oral clonidine stimulation test. He required hospitalization. The authors of this case report suspect that clonidine may have caused acute pulmonary artery vasoconstriction (directly), which could have decreased pulmonary blood flow, producing relative pulmonary hypoxemia, setting off an asthma attack.

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