HTN Pharmacology

Mechanisms of action of drugs for HTN:
  • Decrease preload (fluid volume), SVR and force of cardiac contraction.
  • Block cardiovascular response to catecholamines
  • Block outflow of catecholamines 
Drug class
Mechanism
Side effects & considerations
Thiazide diuretics: HCTZ (hydrodiuril)
Promotes H2O & Na+ excretion; reduces SVR. First-line tx.
K+, glucose & triglycerides
Angiotensin-converting enzyme (ACE)inhibitors 
(“-pril” drugs)
Blocks formation of angiotensin II; prevents vasoconstriction & Na+/H2O retention
Dry persistent cough; angioedema; K+ retention; unsafe in pregnancy; first-dose hypotension
Beta-blockers 
(“-lol” drugs)
Blocks  β-1 receptors in heart & vascular smooth muscle
Contraindicated in COPD & asthma; hold for bradycardia. Fatigue; bradycardia; depression.
Rebound HTN if DC’d
Angiotensin receptor blockers (ARBs) (“-sartan”)
Blocks angiotensin II receptors; prevents vasoconstriction & fluid retention
Expensive. For people who do not tolerate ACE-I. Unsafe in pregnancy.  K+
Calcium channel blockers (“-ipine)
Blocks influx of calcium ions in cardiac & vascular cells
Reflex tachycardia; worsens heart failure; hypotension; heart block; constipation. Hold for bradycardia.
Alpha blockers
 (“-zosin)
Blocks alpha adrenergic receptors on vascular smooth muscle
First-dose syncope; orthostatic hypotension & reflex tachycardia
Central sympatholytics: clonidine (Catapres)
Alpha-2 stimulant; inhibits outflow of catecholamines to heart & vessels; vasodilation,  CO
Rebound HTN with abrupt DC of med. Sedation possible. Unsafe in pregnancy. Available TD patch.
Vasodilators: hydralazine (Apresoline)
Acts on peripheral arterioles, causing vasodilation
Injectable available. Monitor HR, pulse. Orthostatic hypotension. Do not DC abruptly.

Which drugs are appropriate?

PreHypertension: lifestyle modifications
Stage 1: diuretic first, maybe add beta blocker or Ace inhibitor
Stage 2: more aggresive tx. more meds
Heart Failure: no calcium channel blockers; Beta blockers used cautiously
African American: Respond better to diuretics and calcium channel blockers
African American & elderly: More sensitive to effects of sodium in diet

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