Vasodilators in the Treatment of Hypertension

Pharmacodynamics:

The drug class of vasodilators treat hypertension by directly vasodilating blood vessels in the periphery. Vasodilators decrease resistance in the blood vessels resulting in a decrease in blood pressure.[1] Direct-acting vasodilators dilate arterioles specifically, without having a dilating effect on the venous system.[2] Although, many antihypertensive drugs ultimately produce vasodilation through a cascade of events, this class antihypertensive drugs produce vasodilation by acting directly on the smooth muscle of the vasculature in the periphery.[3] Specifically, direct-acting vasodilators stimulate intracellular components by activating phosphorylation of cyclic-adenosine monophosphate (cAMP) and cyclic-guanosine monophosphate (cGMP).[1] These cyclic second-messengers inhibit smooth muscle contraction, as well as platelet aggregation.[1]

Pharmacokinetics and Adverse Effects:

However, direct vasodilators are usually not the first in line in the treatment of hypertension. This class of drugs have a fairly short half-life, which requires frequent doses throughout the day.[4] This class of drugs are primarily metabolized by the liver and excreted via the kidneys.[2] While vasodilators are successful in controlling hypertension, these medications possess a myriad of side effects. Reflex tachycardia is the primary adverse effect of these drugs, as a consequence of the medication induced baroreflex response compensating for the sudden medication decrease in vascular resistance. Other less serious side effects include orthostatic hypotension, dizziness, weakness, fluid retention and nausea.[5] PTs should be mindful of potential implications of adverse effects of these drugs or contraindications to therapy in patients.

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References:

  1. 1.0 1.1 1.2 Walter U, Waldmann R, Nieberding M. Intracellular mechanism of action of vasodilators. European Heart Journal. 1988;9(suppl H):1-6. doi:10.1093/eurheartj/9.suppl_h.1.
  2. 2.0 2.1 Cohn JN, Mcinnes GT, Shepherd AM. Direct-Acting Vasodilators. The Journal of Clinical Hypertension. 2011;13(9):690-692.
  3. Carter B, Saseen J. Hypertension. 5th ed. New York , NY: McGraw-Hill; 2002.
  4. Patel P, Jneid H. Interventional Pharmacology-Vasodilators. The Cardiology Advisor. https://www.thecardiologyadvisor.com/cardiology/interventional-pharmacologyvasodilators/article/583886/. Published September 17, 2018. Accessed October 10, 2018.
  5. Ciccone CD. Pharmacology in Rehabilitation. 5th ed. Philadelphia: F.A. Davis Company; 2016.