Direct vasodilation

Vasodilators are drugs causing blood vessels dilatation.

Classification of vasodilators
1. Myotropic


 * coronary – nitrates, nitrites, molsidomine;
 * others – Ca2+ Channel blockers, hydralazines, nitroprusside, minoxidil, diazoxide, purines, nicotine derivatives, others.

2.Neurotropic – α1-lytic


 * non-selective – phentolamine, phenoxybenzamine;
 * selective – prazosin, doxazosin, metazosin.

3. ACEI


 * It is advisable to divide the individual drugs according to the site of action:


 * mainly for arterioles – hydralazines, Ca2+ antagonists, phentolamine, purines, nicotinic acid derivatives, others;
 * mainly for veins – nitrates, molsidomine (at higher doses also arterioles);
 * for arterioles and veins – selective α1-lytic, ACEI, nitroprusside.

Direct vasodilation
They reduce blood pressure by dilating the effect on vascular smooth muscle - thereby reducing peripheral vascular resistance while maintaining compensatory mechanisms mediated by baroreceptors, sympathetic nerves and the renin-angiotensin-aldosterone system ( RAAS ). This fact has its advantages and disadvantages.


 * The advantage is that the vasodilators are not hypotensive, they dilate the renal arterioles, so they do not restrict renal flow . They do not affect sexual function . They can be given during pregnancy.
 * The disadvantages are fluid retention by RAAS activation and the subsequent possible expansion of extracellular volume, undesired reflex tachycardia, and a decrease in the antihypertensive effect due to compensatory effects. The mentioned disadvantages can be balanced by combination with β-lytics (in case of contraindication β-lytics they can be combined with methyldopa, clonidine ). The risk of fluid retention can be avoided by concomitant administration of diuretics.


 * Representatives:


 * Dihydralazine
 * Endralazine
 * Minoxidil
 * Sodium nitroprusside

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