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Topic 6

Part of the FMGE study roadmap. Botany topic pharma-006 of Botany.

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Cardiovascular Pharmacology

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Cardiovascular Pharmacology — Key Facts for FMGE Core concept: Understanding the RAAS system, sympathetic nervous system, and direct vasodilators provides the framework for antihypertensive therapy High-yield point: ACE inhibitors are first-line for hypertension with diabetes (nephroprotective); know their side effect of cough and contraindication in pregnancy ⚡ Exam tip: In heart failure, ACE inhibitors reduce mortality; beta-blockers reduce mortality; diuretics reduce symptoms; digoxin reduces hospitalizations

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Cardiovascular Pharmacology — FMGE Study Guide

Antihypertensive Drugs

Renin-Angiotensin-Aldosterone System (RAAS)

ACE inhibitors (e.g., enalapril, lisinopril, ramipril, captopril):

  • Block conversion of Angiotensin I → Angiotensin II
  • Effects: ↓vasoconstriction, ↓aldosterone → ↓BP; prevents cardiac remodeling; natriuresis
  • Indications: Hypertension, heart failure (reduce mortality), post-MI, diabetic nephropathy
  • Side effects:
    • Dry cough (10-15%) - due to bradykinin accumulation (not ACE for bradykinin)
    • Angioedema (rare but serious) - also bradykinin-mediated
    • Hyperkalemia (↓aldosterone → ↓K excretion)
    • First-dose hypotension
    • Teratogenicity - contraindicated in pregnancy (fetal renal damage)
  • ACEi are nephroprotective: Dilates efferent arteriole → ↓intraglomerular pressure

Angiotensin Receptor Blockers (ARBs) (e.g., losartan, valsartan, telmisartan):

  • Block AT1 receptor (where AngII acts)
  • Advantages over ACEi: No cough (don’t affect bradykinin); angioedema less common
  • Same teratogenicity risk as ACEi
  • Indications: Same as ACEi; used when ACEi not tolerated

Direct renin inhibitors (Aliskiren):

  • Blocks renin’s active site
  • Less effective than ACEi/ARBs in combination

Beta-Blockers

For hypertension (not first-line alone anymore, but useful in specific populations):

  • Cardioselective (β1 > β2): Metoprolol, atenolol, bisoprolol
  • Non-selective: Propranolol, carvedilol (α1 + β)

Indications: Hypertension with heart disease, post-MI, angina, arrhythmias, heart failure (bisoprolol, carvedilol, metoprolol succinate)

Calcium Channel Blockers

Dihydropyridines (DHP) (e.g., amlodipine, nifedipine, felodipine):

  • Primarily act on vascular smooth muscle → vasodilation
  • No direct cardiac effect at therapeutic doses (less reflex tachycardia with long-acting)
  • Used for hypertension, angina
  • Side effects: Peripheral edema (arteriolar dilation vs capillary recruitment), flushing, headache

Non-DHPs (e.g., verapamil, diltiazem):

  • Act on heart (↓HR, ↓conductivity) and vessels
  • Verapamil: More cardiac depression; used for angina, arrhythmias, migraine
  • Diltiazem: Intermediate; used for angina, hypertension, arrhythmias
  • Side effects: Constipation (verapamil), bradycardia, heart block, negative inotropy

Diuretics

Thiazides (e.g., hydrochlorothiazide, chlorthalidone):

  • Inhibit Na-Cl cotransporter in DCT
  • First-line for hypertension (especially with osteoporosis - calcium-sparing)
  • Side effects: Hypokalemia, hyperuricemia, hypercalcemia, hyperglycemia, hyponatremia

Loop diuretics (e.g., furosemide, bumetanide):

  • Inhibit NKCC2 in thick ascending limb
  • Used for heart failure edema, renal impairment, hypertension (if GFR <30)

Potassium-sparing (spironolactone, eplerenone, amiloride, triamterene):

  • Spironolactone/Eplerenone: Aldosterone antagonists (MR antagonists) - used in heart failure (mortality reduction), resistant hypertension
  • Amiloride/Triamterene: Block ENaC directly
  • Used to counteract hypokalemia from thiazides/loop diuretics

Central Alpha-2 Agonists

Clonidine:

  • Stimulates α2 in brainstem → ↓sympathetic outflow → ↓BP
  • Side effects: Sedation, dry mouth, rebound hypertension on abrupt cessation
  • Used for resistant hypertension, opioid withdrawal, anesthesia adjunct

Methyldopa:

  • Prodrug → α-methyldopamine → α-methylnorepinephrine (α2 agonist)
  • Safe in pregnancy (used for pregnancy-induced hypertension/preeclampsia)
  • Side effects: Sedation, hepatotoxicity, positive Coombs test (autoimmune hemolytic anemia)

Direct Vasodilators

Hydralazine:

  • Relaxes arteriolar smooth muscle → ↓SVR
  • Used with isosorbide dinitrate in heart failure (especially in African Americans, or when ACEi/ARB not tolerated)
  • Side effects: Reflex tachycardia, lupus-like syndrome (SLE-like), fluid retention

Minoxidil:

  • K+ channel opener → potent vasodilation
  • Reserved for severe/resistant hypertension
  • Side effects: Hirsutism (used as topical for baldness), fluid retention, tachycardia

Sodium nitroprusside:

  • NO donor; potent vasodilator (both arteriolar and venous)
  • Used for hypertensive emergency
  • Side effects: Cyanide toxicity (thiosulfate is antidote), severe hypotension
  • Must be given in ICU with arterial pressure monitoring

Drug Therapy for Specific Conditions

Hypertension with diabetes: ACEi or ARB (nephroprotective) Hypertension with heart failure: ACEi + beta-blocker + diuretic + spironolactone Hypertension with BPH: Alpha-1 blocker (tamsulosin) Hypertension in pregnancy: Methyldopa, labetalol, nifedipine Hypertensive emergency: IV nicardipine, labetalol, nitroprusside

Heart Failure Drugs

ACE Inhibitors / ARBs

  • Reduce mortality and hospitalizations
  • Prevent adverse cardiac remodeling
  • First-line therapy for HFrEF (heart failure with reduced ejection fraction)

Beta-Blockers

  • Bisoprolol, Carvedilol, Metoprolol succinate reduce mortality in HFrEF
  • Start low, go slow; contraindicated in acute decompensated HF

Diuretics

  • Furosemide: Symptomatic relief (reduce volume overload)
  • Thiazides for mild HF; loop for severe
  • Spironolactone for HFrEF (mortality benefit - aldosterone antagonists)

Aldosterone Antagonists

  • Spironolactone/Eplerenone: Reduce mortality in HFrEF (RALES trial - 30% reduction in death)
  • Monitor potassium (hyperkalemia risk)

Digoxin

  • Positive inotrope (inhibits Na-K ATPase → ↑intracellular Na → ↓Na-Ca exchange → ↑Ca in cell → ↑contractility)
  • Reduces hospitalizations (not mortality)
  • Narrow therapeutic index - toxicity common
  • Toxicity: Nausea, vomiting, visual changes (yellow-green halos), arrhythmias (AV block, premature ventricular contractions, bigeminy), confusion

Newer Agents

  • ARNI (Angiotensin Receptor-Neprilysin Inhibitor): Sacubitril/valsartan (Entresto) - neprilysin degrades natriuretic peptides; sacubitril blocks neprilysin → ↑natriuretic peptides → beneficial in HF
  • SGLT2 inhibitors (dapagliflozin, empagliflozin): Originally for diabetes; now for heart failure regardless of diabetes status

Antiarrhythmic Drugs

Class I (Na channel blockers)

Class IA: Quinidine, Procainamide, Disopyramide

  • Block Na channels + some K channel blockade
  • Prolong action potential (class III-like effect)
  • Side effects: QT prolongation (Torsades de Pointes), lupus with procainamide

Class IB: Lidocaine, Mexiletine

  • Preferentially block ischemic/rapidly firing tissue
  • Shorten action potential
  • Use: Ventricular arrhythmias, especially in ischemic tissue

Class IC: Flecainide, Propafenone

  • Do not use in structural heart disease/ischemia (PRODIGY trial - increased mortality)
  • Used for atrial fibrillation, SVT

Class II (Beta-blockers)

  • Esmolol (IV), propranolol, metoprolol
  • Slow HR, ↓AV conduction, anti-ischemic
  • Used for rate control in AF, SVT, arrhythmias

Class III (K channel blockers)

  • Amiodarone: Multi-channel blocker (Na, K, Ca, beta-blocker); used for ventricular arrhythmias, AF; very effective but many side effects (pulmonary fibrosis, hepatotoxicity, thyroid dysfunction, corneal deposits, blue-grey skin, QT prolongation)
  • Sotalol: K channel blocker + beta-blocker; Torsades risk
  • Dofetilide: Pure K channel blocker; Torsades risk
  • Ibutilide: IV for acute AF termination

Class IV (Ca channel blockers)

  • Verapamil, Diltiazem: Block L-type Ca channels
  • Slow SA node, slow AV conduction
  • Used for PSVT, rate control in AF

Adenosine

  • Purinergic receptor agonist (A1) → ↑K conductance, ↓Ca
  • IV adenosine: Used to terminate acute SVT (diagnostic and therapeutic)
  • Very short half-life (seconds)
  • Side effects: Flushing, chest discomfort, bronchospasm (avoid in asthma)

Digoxin

  • Increases vagal tone to AV node
  • Slows ventricular rate in AF
  • Narrow TI - toxicity common

Anti-Anginal Drugs

Nitrates (Nitroglycerin, Isosorbide dinitrate)

  • NO donor → vasodilation (venous > arterial)
  • ↓Preload → ↓myocardial O2 demand
  • Dilate coronary arteries (relieve spasm)
  • Uses: Acute angina (sublingual), prevention (extended-release), MI (IV nitroglycerin)
  • Side effects: Headache, hypotension, reflex tachycardia, tolerance (lose effect after 24 hours continuous - need nitrate-free period)

Beta-Blockers

  • ↓HR, ↓contractility, ↓BP → ↓myocardial O2 demand
  • First-line for chronic stable angina
  • Shown to reduce mortality post-MI

Calcium Channel Blockers

  • Vasodilation (DHP) + ↓HR (verapamil, diltiazem)
  • Used when beta-blockers contraindicated or as add-on therapy

Ranolazine

  • Late Na channel blocker → reduces diastolic tension → ↓angina
  • Used as add-on therapy when first-line agents insufficient

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