Clonidine

Mechanism of action:

It causes activation of α2 receptors in the vasomotor center of brain that causes a decrease in sympathetic outflow to the peripheral vascular bed.

Actions:
Its intravascular injection causes a direct activation of peripheral α-adrenergic receptors resulting in a short time elevated systolic and diastolic pressure. After this, there is a reduction of cardiac output and cardiac rate resulting in the fall of blood pressure.

It causes a decrease in plasma renin activity.

It causes an elevated vagal discharge along with promoted baroreceptor reflex sensitivity.

It causes a reduction of renal vascular resistance but does not affect renal blood flow.

It causes sodium and water retention and that is why they are taken along with diuretics.

Pharmacokinetics:
It is well absorbed orally and is excreted by the kidney.

Therapeutic uses:
It is used for hypertensive patients especially in patients of renal impairment.

Adverse effects:
Sedation, drowsiness, drying of the nasal mucosa, fluid retention, headache and sweating,

Dosage:
It may be given in the dose of 0.2-1.2 mg/day. Its transdermal patches can give dose for up to 1 week.