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

Links

Related articles

• Treatment of ischemic heart disease
• Antihypertensives
• Renin-Angiotensin-Aldosterone system
• Angiotensin II receptor blockers
• Hypertension
• Hypertensive crisis

Source

• MARTÍNKOVÁ, Jiřina – MIČUDA, Stanislav – CERMANOVÁ, Jolana. Vybrané kapitoly z klinické farmakologie pro bakalářské studium : Kardiovaskulární systém [online]. ©2000. [cit. 2010-07-01]. <https://www.lfhk.cuni.cz/farmakol/predn/bak/kapitoly/prednasky/kardio-bak.ppt/>.