Clonidine

Its major haemodynamic effects result from action on central sites in medulla (vasomotor centre) and hypothalamus. It stimulates alpha 2 receptors present at these sites leading to decrease in sympathetic outflow, resulting in fall in BP and bradycardia.

Indications

All grades of hypertension (except pheochromocytoma).

Dosage

0.05-0.1 mg thrice daily increasing gradually every 2nd or 3rd day.

Contra-Indications

Sick-sinus syndrome.

Special Precautions

While discontinuing, reduce dose gradually, abrupt withdrawal in patients on high doses may result in severe rebound hypertension. Pregnancy, lactation, hepatic & renal insufficiency, not to drive vehicles or engage in hazardous occupations.

Side Effects

Sedation, dry mouth, dizziness, constipation, sleep disturbances, impotence & allergic manifestations.

Drug Interactions

Hypnosedatives, antihistamines & alcohol may cause excessive drowsiness. Hypotensive action may be potentiated by tricyclic anti-depressants, diuretics and vasodialators . Effects of clonidine antagonised by centrally acting alpha-blockers . Antagonise oral hypoglycaemics.