- Pharmshala

Drugs Used in Congestive Heart Failure

What goes wrong in heart failure, and the drug classes — ACE inhibitors, beta-blockers, diuretics, digoxin and more — used to treat it.

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What goes wrong in heart failure

In congestive heart failure (CHF), the heart can no longer pump enough blood to meet the body’s needs. The fall in cardiac output triggers compensatory neurohormonal responses — sympathetic activation and activation of the renin–angiotensin–aldosterone system (RAAS) — which help in the short term but, sustained over time, raise the heart’s preload and afterload and drive further decline: a vicious cycle.

Falling cardiac output triggers sympathetic and RAAS activation, which raise preload and afterload and push the failing heart to work even harder.

Drug treatment of CHF is therefore aimed at breaking this cycle: reducing the workload on the heart, blocking the harmful neurohormonal pathways, and in some cases directly boosting contractility.

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Drug classes used in CHF

Class	Examples	What it does
ACE inhibitors	Enalapril, ramipril, lisinopril	Block the conversion of angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone-driven fluid retention. First-line in CHF; improve survival.
ARBs	Losartan, valsartan	Block the AT₁ receptor directly; used when ACE inhibitors cause a persistent dry cough.
Beta-blockers	Bisoprolol, carvedilol, metoprolol succinate	Blunt chronic sympathetic overdrive; started at a low dose and up-titrated slowly, since beta-blockade can transiently worsen acute failure.
Diuretics	Furosemide (loop), spironolactone (aldosterone antagonist)	Reduce preload by removing excess salt and water; relieve congestion (breathlessness, oedema). Spironolactone also blocks aldosterone’s harmful remodelling effects and improves survival.
Cardiac glycosides	Digoxin	Inhibits the myocyte Na⁺/K⁺-ATPase, raising intracellular Na⁺ and, via the Na⁺/Ca²⁺ exchanger, intracellular Ca²⁺ — a positive inotrope. Also slows AV conduction (useful if CHF coexists with atrial fibrillation). Narrow therapeutic index.
Vasodilators	Hydralazine + isosorbide dinitrate	Reduce afterload (hydralazine, arteriolar) and preload (nitrate, venous); an alternative in patients who cannot tolerate ACE inhibitors/ARBs.
SGLT2 inhibitors	Dapagliflozin, empagliflozin	Originally anti-diabetic; now shown to reduce CHF hospitalisation and mortality by mechanisms still being worked out (natriuresis, metabolic effects).

Digoxin toxicity

Because digoxin has a narrow therapeutic index, toxicity is a classic exam topic: nausea, vomiting, visual disturbance (yellow–green halos), and arrhythmias. Hypokalaemia increases digoxin binding to the Na⁺/K⁺-ATPase and worsens toxicity.