Clonidine hydrochloride tablets for treating hypertension in adults

Clonidine hydrochloride tablets are oral antihypertensive medications available in 0.1 mg, 0.2 mg, and 0.3 mg strengths. They act on receptors in the brain to reduce blood pressure by decreasing sympathetic nervous system activity, lowering heart rate, and reducing peripheral resistance.

Clonidine hydrochloride tablets are used to treat hypertension in adult patients. They may be prescribed alone or in combination with other blood pressure medications.

Clonidine hydrochloride

Clonidine stimulates alpha-adrenoreceptors in the brainstem, which reduces sympathetic nervous system outflow. This leads to decreased peripheral resistance, renal vascular resistance, heart rate, and blood pressure. The drug lowers blood pressure relatively quickly, with effects observable within 30 to 60 minutes after oral dosing, reaching maximum effect in 2 to 4 hours.

Adults

The initial dose is typically one 0.1 mg tablet twice daily (morning and bedtime). Dosage may be increased by 0.1 mg increments weekly based on blood pressure response, with most effective doses ranging from 0.2 mg to 0.6 mg daily divided into two doses. Up to 2.4 mg daily is considered the maximum effective dose but higher doses are rarely used.

Elderly and Renal Impairment

Lower initial doses may be beneficial for elderly patients and those with impaired renal function, with careful monitoring recommended. Since hemodialysis removes minimal clonidine, supplemental dosing after dialysis is usually unnecessary.

Clonidine hydrochloride tablets are contraindicated in patients with known hypersensitivity to clonidine.

Withdrawal

Do not stop clonidine abruptly without consulting a physician. Sudden discontinuation can cause nervousness, agitation, headache, tremor, and rapid increases in blood pressure, potentially leading to serious complications like hypertensive encephalopathy and stroke. Dose reduction should be gradual over 2 to 4 days. Patients on beta-blockers require withdrawal of the beta-blocker several days before discontinuing clonidine.

Other Warnings

• Monitor for bradycardia and AV block, especially when used with other sympatholytic drugs.
• No expected benefit in hypertension caused by pheochromocytoma.
• Continue clonidine until four hours before surgery and resume as soon as possible postoperatively with blood pressure monitoring.
• Patients should be cautious about sedation, dizziness, or visual accommodation disturbances; avoid hazardous activities until effects are known.
• Concomitant use with alcohol, barbiturates, or other sedating drugs can enhance sedation.

Common side effects (dose-related)

• Dry mouth (~40%)
• Drowsiness (~33%)
• Dizziness (~16%)
• Constipation (~10%)
• Sedation (~10%)

Less common or reported adverse reactions

• Fatigue, headache, pallor
• Bradycardia, congestive heart failure, arrhythmias
• Agitation, hallucinations, depression
• Skin reactions including rash and urticaria
• Gastrointestinal symptoms like nausea and abdominal pain
• Sexual dysfunction, urinary retention
• Thrombocytopenia
• Gynecomastia, weight gain
• Dryness of nasal mucosa and eyes, blurred vision

• Potentiates CNS depression when used with alcohol, barbiturates or other sedating drugs.
• Tricyclic antidepressants may reduce clonidine's blood pressure-lowering effect, possibly requiring higher clonidine doses.
• Neuroleptics can exacerbate orthostatic hypotension and related symptoms.
• Concomitant use with agents affecting heart conduction (digitalis, calcium channel blockers, beta-blockers) requires heart rate monitoring due to risk of severe bradycardia and heart block.
• Clonidine combined with amitriptyline can cause corneal lesions in animal studies; clinical relevance unclear.
• High intravenous doses of clonidine may increase arrhythmia risk when combined with haloperidol, relevance to oral use is unestablished.

Pregnancy

Animal studies show no teratogenic effects in rabbits at doses up to 3 times the human dose; however, some studies in rats showed increased fetal resorptions at certain doses. No adequate and well-controlled human studies exist. Clonidine crosses the placenta and should be used in pregnancy only if clearly needed. Pregnancy category C.

Lactation

Clonidine is excreted in human milk; caution is advised when administering to nursing women.

Overdose may cause early hypertension followed by hypotension, bradycardia, respiratory depression, hypothermia, CNS depression, and miosis. Large overdoses can lead to cardiac conduction defects, apnea, coma, and seizures. Symptoms appear within 30 minutes to 2 hours of ingestion. In children, as little as 0.1 mg can cause toxicity.

There is no specific antidote. Supportive care includes gastric lavage if recent ingestion, activated charcoal, atropine for bradycardia, intravenous fluids or vasopressors for hypotension, and vasodilators for hypertension. Naloxone may be used adjunctively but blood pressure must be monitored due to risk of paradoxical hypertension. Dialysis is not effective for elimination.

Store at 256C (776F); permitted excursions 156 to 306C (596 to 866F). Dispense in a tight, light-resistant container.