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Chapter 46

Chapter 46. Vasodilators. Vasodilation. Can be produced with a variety of drugs Some act primarily on veins or arterioles, and some act on both types of vessels Wide variety of therapeutic applications. Basic Concepts in Vasodilator Pharmacology. Selectivity of vasodilatory effects

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Chapter 46

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  1. Chapter 46 Vasodilators

  2. Vasodilation • Can be produced with a variety of drugs • Some act primarily on veins or arterioles, and some act on both types of vessels • Wide variety of therapeutic applications

  3. Basic Concepts in Vasodilator Pharmacology • Selectivity of vasodilatory effects • Selective dilation of arterioles • Hydralazine • Selective dilation of veins • Nitroglycerin • Dilate arterioles and veins • Prazosin

  4. Hemodynamic Effects • Drugs that dilate resistance vessels (arterioles) cause a decrease in cardiac afterload • Drugs that dilate capacitance vessels (veins) reduce the force with which blood is returned to the heart, thus reducing preload

  5. Overview of Therapeutic Uses • Principal indications • Essential hypertension • Hypertensive crisis • Angina pectoris • Heart failure • Myocardial infarction • Pheochromocytoma • Peripheral vascular disease • Pulmonary arterial hypertension • Production of controlled hypotension during surgery

  6. Vasodilators • Adverse effects related to vasodilation • Postural hypotension • Reflex tachycardia • Expansion of blood volume

  7. Hydralazine (Apresoline) • Selective dilation of arterioles • Mechanism is unknown • Postural hypotension is minimal • Therapeutic uses • Essential hypertension • Hypertensive crisis • Heart failure

  8. Hydralazine (Apresoline) • Adverse effects • Reflex tachycardia • Increased blood volume • Systemic lupus erythematosus–like syndrome • Headache, dizziness, weakness, and fatigue • Drug interactions • Other antihypertensive agents • Avoid excessive hypotension • Combined with beta blocker to protect against reflex tachycardia and diuretics to prevent sodium and water retention and expansion of blood volume

  9. Minoxidil (Loniten) • Selective dilation of arterioles • More intense dilation than hydralazine, but causes more severe adverse reactions • Used for severe hypertension that is unresponsive to safer drugs • Adverse effects • Reflex tachycardia • Sodium and water retention • Hypertrichosis • Pericardial effusion • Other

  10. Sodium Nitroprusside (Nitropress) • Fastest-acting antihypertensive agent • Causes venous and arteriolar dilation • Administration: IV infusion • Onset: immediate (BP returns to pretreatment level in minutes when stopped) • Used for hypertensive emergencies • Adverse effects • Excessive hypotension • Cyanide poisoning • Thiocyanate toxicity

  11. Fig. 46–1. Structure and metabolism of sodium nitroprusside.

  12. Other Vasodilators • Angiotensin-converting enzyme (ACE) inhibitors • Angiotensin II receptor antagonists • Direct renin inhibitors • Organic nitrates • Calcium channel blockers • Sympatholytics • Alpha-adrenergic blocking agents • Ganglionic blocking agents • Adrenergic neuron blocking agents • Centrally acting agents • Nesiritide • Drugs for pulmonary arterial hypertension

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