CH. 49 Vasodilators

Drugs that dilate arterioles cause:

Decrease in cardiac afterload

• Drugs that dilate veins (capacitance vessels) cause:

• reduced preload by reducing the force that blood is returned to the heart

Hydralazine

selectively dilates arterioles, used for essential hypertension, hypertensive crisis, and heart failure.

Adverse effect of hydralazine

reflex tachycardia, increased blood volume, and systemic lupus erythematosus-like syndrome.

Headache, dizziness, weakness, and fatigue

Drug interactions with 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]

Selectively dilates arterioles, more intense dilation of arterioles than hydralazine causes more adverse effects

Therapeutic use of minoxidil

Treating severe hypertension unresponsive to other safer medications.

Adverse effects of minoxidil

• Reflex tachycardia

• Sodium and water retention

• Hypertrichosis: excessive hair growth 

• Pericardial effusion: excess fluid accumulates in the pericardium

which drug can you use to treat the adverse effects of Minoxidil

Lasix (furosemide)

Nitroglycerin

A medication that selectively dilates veins, commonly used for angina pectoris.

Prazosin

A drug that dilates both veins and arteries.

Sodium Nitroprusside

The fastest acting antihypertensive agent that causes dilation of arterioles and veins, administered through IV.

Therapeutic uses of Sodium Nitroprusside

Hypertensive emergencies

Adverse effects of Sodium Nitroprusside

• Excessive hypotension

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

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

Other Therapeutic uses of vasodilators

Myocardial infarction

Pheochromocytoma: tumor in the adrenal glands 

Reflex tachycardia

An increase in heart rate that can occur as a compensatory response to vasodilators.

Essential hypertension

A condition treated by vasodilators characterized by high blood pressure with no identifiable cause.

Controlled hypotension during surgery

A therapeutic use of vasodilators to maintain lower blood pressure during surgical procedures.

Peripheral vascular disease

A condition that can be treated with vasodilators, characterized by reduced blood flow to limbs.