Overview
Clonidine is a centrally-acting alpha-2 adrenergic agonist used primarily for the treatment of hypertension. It reduces sympathetic outflow from the central nervous system, leading to decreased peripheral vascular resistance and heart rate. The medication is available in oral tablet formulations and requires careful dose titration and gradual discontinuation to avoid withdrawal effects.
Mechanism of Action
Clonidine stimulates alpha-2 adrenergic receptors in the brainstem, reducing sympathetic outflow from the central nervous system. This results in decreased peripheral vascular resistance, reduced heart rate, and lowered blood pressure through inhibition of norepinephrine release.
Indications
- Treatment of hypertension
- May be used alone or in combination with other antihypertensive agents
Common Doses
- 0.1 mg
- 0.2 mg
- 0.3 mg
Dosage
Initial dose: 0.1 mg twice daily (morning and bedtime). Dose may be increased by 0.1 mg per day at weekly intervals as needed. Therapeutic range: 0.2-0.6 mg daily in divided doses, with maximum effective dose of 2.4 mg daily. Elderly patients and those with renal impairment may require lower initial doses.
Contraindications
- Known hypersensitivity to clonidine
Side Effects
- Dry mouth (40%)
- Drowsiness (33%)
- Dizziness (16%)
- Constipation (10%)
- Sedation (10%)
- Fatigue, headache, weakness
- Bradycardia, orthostatic hypotension, syncope
- Insomnia, depression, hallucinations, vivid dreams
- Rash, pruritus, urticaria
- Nausea, vomiting, hepatitis
- Sexual dysfunction, urinary retention
- Thrombocytopenia
- Weight gain, gynecomastia
- Blurred vision, dry eyes
Interactions
- Beta-blockers: Increased risk of rebound hypertension upon discontinuation
- CNS depressants: Additive sedative effects
- Tricyclic antidepressants: May reduce antihypertensive effect
- Alcohol: Increased sensitivity and CNS depression
Counseling Points
- Do not stop taking suddenly - work with your doctor to taper dose gradually
- Take larger portion of daily dose at bedtime to minimize daytime drowsiness
- May cause dry mouth, dizziness, or drowsiness - use caution when driving or operating machinery
- Rise slowly from sitting/lying position to avoid dizziness
- Avoid alcohol as it may increase side effects
- Monitor blood pressure regularly
- Keep medication out of reach of children - small doses can be toxic in pediatric patients