Prazosin, Terazosin and Doxazosin

Mechanism of action:

It selectively blocks postsynaptic α1 adrenergic receptors.

Actions:
It causes the dilatation of the resistance vessels as well as capacitance vessels. This results in reduced blood pressure in upright position.

Its long term use may cause water and salt retention. This effect can be reduced by using diuretics.

Therapeutic uses:
1. It is used for mild to moderate chronic hypertension. It is even more useful on combination with diuretic or propranolol.
2. It is also used for acute congestive cardiac failure.
3. To relieve urinary obstruction (Terazosin).

Adverse effects:
It may cause dizziness, headache, lassitude, nasal congestion, postural hypotension, retention of salt and fluid.