Aldosterone antagonists (MRAs)
also: spironolactone · eplerenone · amiloride
Overview
Potassium-sparing diuretics. MRAs are prognostic in heart failure and key in resistant hypertension and primary hyperaldosteronism.
Mechanism
Spironolactone/eplerenone competitively antagonise the mineralocorticoid (aldosterone) receptor in the distal nephron → ↓Na⁺ reabsorption, K⁺ retention. Amiloride directly blocks the epithelial Na⁺ channel (ENaC). All are K⁺-sparing.
Indications
- Heart failure (HFrEF) — prognostic (spironolactone/eplerenone)
- Resistant hypertension (step 4, if K⁺ ≤4.5)
- Primary hyperaldosteronism / Conn
- Ascites in cirrhosis (spironolactone)
The agents
active metabolites
Anti-androgen effects → gynaecomastia.
OD/BD
Less gynaecomastia — use if spironolactone not tolerated.
OD
Often combined with a thiazide/loop to offset K⁺ loss.
Adverse effects
Spironolactone (anti-androgen); switch to eplerenone.
Cautions & contraindications
Interactions
- ACEi/ARB → additive hyperkalaemia (monitor closely)
- K⁺ supplements
- NSAIDs
Monitoring & kinetics
Serum K⁺ + renal function (before, and after starting/uptitration)
Oral. Caution combining with any other RAAS agent.
Source: BNF — Aldosterone antagonists