Cardiovascular Drugs and Medications Q 36
Raymund is reviewing cardiovascular drugs for his upcoming exam. For a well-prepared student, he should know that vasodilators are agents that:
A. Relax smooth muscles.
B. Are used to treat hypotension.
C. Stimulate the adrenergic receptors of peripheral sympathetic nerves.
D. Cause respiratory depression.
Correct Answer: A. Relax smooth muscles.
Vasodilators relax smooth muscle. Vasodilators dilate or prevent constriction of the blood vessels, which allow greater blood flow to various organs in the body. Many vasodilators bind to receptors on endothelial cells of the blood vessel, which stimulate calcium release. Calcium activates the enzyme nitric oxide synthase (NO synthase) and converts L-arginine into NO. It leaves the endothelial cell via diffusion and enters vascular smooth muscle cells. NO activates GTP and converts it into cGMP. cGMP then stimulates myosin-light chain phosphatase, which removes a single phosphate from myosin and actin filaments. The dephosphorylation of myosin and actin filaments allows vascular smooth muscle relaxation.
Option B: They are used to treat hypertension, not hypotension. Vasodilators are useful in treating a variety of medical conditions, most commonly systemic hypertension. Other diseases include myocardial infarction (both ST-segment elevation and non-ST-segment elevation), angina, heart failure, stroke, chronic kidney disease, preeclampsia, hypertensive emergency.
Option C: Stimulating the adrenergic receptors of peripheral sympathetic nerves causes blood vessels to contract. Nitrates increase the amount of nitric oxide in vascular smooth muscle cells, causing vasodilation. Nitrates dilate veins more than arteries and decrease preload.
Option D: Respiratory depression is not an action of vasodilators. Respiratory depression is among the more serious adverse reactions with opiate use that is especially important to monitor in the postoperative patient population.