DIRECT ACTING VASODILATORS
direct acting vasodilators drugs are the drugs used primarily for acute hypertensive crisis. as what the name indicates the effect of these drugs on blood vessels is "direct" means they directly interact with smooth muscles of the vessels with only few intermediates and thus dilate blood vessels.
these drugs are very powerful and potent against hypertension that sometimes the adverse effect can become hypo-tension for a hypertensive patient.
for that reason their use is not generally in chronic hypertensions rather they are used primarily in acute cases like before or during surgery ,acute hypertensive shock etc.
classification of direct acting vasodilators
depending upon their pharmacological action direct vasodilators are classified into the following two classes
- arteriolar dilators
- arteriolar + venular dilators
arteriolar dilators
these drugs bring vasodilation only in resistant vessels arteries.
they include hydralazine, minoxidil, finoldopam etc.
arteriolar + venular dilators
The vasodilatation effect of these drugs applies to both arterial side and venous side of blood vessels.sodium nitroprusside is an example.
Mechanism of action of direct vasodilators
the pharmacodynamics of vasodilators are generally following the same principles but not exactly the same one. the basic mechanism in their effect on smooth muscles interacting with myosin fibers of smooth muscles to bring about vasodilatation.
