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CH. 49 Vasodilators

Basic Concepts of vasodilators 

  • Selective vasodilatory effects 

  • Hydralazine selectively dilates arterioles 

  • Nitroglycerin selectively dilates veins 

  • Dilates both veins and arteries (Prazosin)

Hemodynamic effects of vasodilators  

  • Drugs that dilate arterioles (resistance vessels) cause a decrease in cardiac afterload 

  • Drugs that dilate veins (capacitance vessels) reduce preload by reducing the force that blood is returned to the heart 

Therapeutic uses of of vasodilators

  • Essential hypertension

  • Hypertensive crisis

  • Angina pectoris 

  • Heart failure

  • Myocardial infarction

  • Pheochromocytoma: tumor in adrenal glands 

  • Peripheral vascular disease

  • Pulmonary arterial hypertension

  • Production of controlled hypotension during surgery

Adverse effects of vasodilators

  • postural hypotension

  • Reflex tachycardia

  • Expansion of blood volume 


  • Hydralazine [Apresoline]

Overall effects and MOA

  • Selectively dilates arterioles 

  • Postural hypotension minimal 

Therapeutic uses of hydralazine 

  • Essential hypertension

  • Hypertensive crisis

  • Heart failure 

Adverse effects of hydralazine 

  • Reflex tachycardia

  • Increased of blood volume 

  • Systemic lupus erythematosus- like syndrome 

  • Headache, dizziness, weakness, and fatigue 

Drug interactions of hydralazine 

  • Other hypertensive agents 

(+) combine with beta blockers to prevent against reflex tachycardia

(+) use diuretics to prevent sodium and water retention (lessen expansion of blood volume.)


  • Minoxidil [Apresoline]

Overall effects and MOA

  • Selectively dilates arterioles 

  • More intense dilation of arterioles than hydralazine, causes more adverse effects

Therapeutic uses of minoxidil

  • Severe hypertension unresponsive to other safer drugs 

Adverse effects of minoxidil

  • Reflex tachycardia

  • Sodium and water retention

  • Hypertrichosis: excessive hair growth 

  • Pericardial effusion: excess fluid accumulates in the pericardium 


  • Sodium Notroprusside [Nitropress]

Overall effects and MOA

  • Fastest acting antihypertensive agent 

  • dilation of arterioles and veins 

  • Administered through IV

  • Immediate onset (BP returns to pretreatment level in minutes when stopped)

Therapeutic uses of Sodium Notroprusside

  • Hypertensive Emergencies (surgery and ICU)

Adverse effects of Sodium Notroprusside

  • Excessive hypotension

  • Cyanide poisoning: Sodium Notroprusside combines with hemoglobin and metabolizes into cyanide 

  • Thiocyanate toxicity Sodium Nitroprusside combines with hemoglobin and metabolizes into thiocyanate