Amiloride Dosage for Hypertension
For adults with hypertension, amiloride should be started at 5 mg daily (taken with food) and can be titrated to 10 mg daily if needed, with careful monitoring of serum potassium levels. 1
Standard Dosing Protocol
Initial Therapy
- Starting dose: 5 mg once daily with food 1
- Add to existing antihypertensive regimen (typically when used as add-on therapy for resistant hypertension)
- Monitor electrolytes shortly after initiation
Dose Titration
- If blood pressure remains uncontrolled after initial period, increase to 10 mg daily 1
- More than 10 mg daily (two 5 mg tablets) is usually not needed 1
- If persistent hypokalemia is documented with 10 mg, the dose can be increased to 15 mg, then 20 mg, with careful monitoring of electrolytes 1
Evidence-Based Context for Use
Role in Resistant Hypertension
Amiloride functions as an epithelial sodium channel (ENaC) blocker in the distal collecting duct, acting as an indirect aldosterone antagonist. In resistant hypertension studies, amiloride 10 mg daily reduced systolic/diastolic blood pressure by 12.2/4.8 mm Hg when added to existing two-drug regimens 2.
The most compelling dosing evidence comes from studies showing:
- Amiloride 2.5 mg combined with hydrochlorothiazide 25 mg lowered BP by 31/15 mm Hg in patients with low-renin hypertension 2
- When this combination was doubled (amiloride 5 mg/HCTZ 50 mg), an additional 11/4 mm Hg reduction occurred 2
- Amiloride 10 mg daily as monotherapy showed comparable efficacy to spironolactone 25 mg in African-American patients 2
Recent Trial Evidence
The 2025 SPARE trial provides the highest-quality recent evidence, demonstrating that amiloride 5-10 mg daily was noninferior to spironolactone 12.5-25 mg for resistant hypertension, with mean home SBP reductions of -13.6 mm Hg vs -14.7 mm Hg respectively 3. This trial used force-titration: starting at 5 mg daily, then increasing to 10 mg daily at 4 weeks if home SBP remained ≥130 mm Hg and serum potassium was <5.0 mmol/L.
Critical Safety Considerations
Hyperkalemia Monitoring
Close monitoring of serum potassium is essential, particularly in high-risk patients 2:
- Older adults
- Patients with diabetes mellitus
- Chronic kidney disease (especially GFR <45 mL/min/1.73 m²)
- Concurrent use with ACE inhibitors, ARBs, or NSAIDs
- Baseline serum potassium >4.5 mmol/L 4
In the SPARE trial, only one patient (0.8%) discontinued amiloride due to hyperkalemia 3, suggesting good tolerability at standard doses with appropriate monitoring.
Advantages Over Spironolactone
- No gynecomastia or breast tenderness (common with spironolactone, especially in men) 2, 3
- No menstrual irregularities
- May be more effective in patients with higher BMI and lower aldosterone-renin ratios 5
Clinical Algorithm for Dosing
- Start with 5 mg daily (with food) when adding to existing antihypertensive regimen
- Check electrolytes within 1-2 weeks of initiation
- Reassess BP at 4 weeks:
- If BP controlled and K+ <5.0 mmol/L: continue current dose
- If BP uncontrolled and K+ <5.0 mmol/L: increase to 10 mg daily
- If K+ ≥5.5 mmol/L: discontinue or reduce dose
- Recheck electrolytes 1-2 weeks after any dose increase
- Doses >10 mg daily rarely needed and require intensive electrolyte monitoring
When to Use Amiloride
Based on current guidelines, amiloride is most appropriate as:
- Fourth-line therapy for resistant hypertension (uncontrolled on 3 drugs including RAS blocker, CCB, and thiazide diuretic) 6, 7
- Alternative to spironolactone when mineralocorticoid receptor antagonist side effects are intolerable 5, 3
- Combination with thiazide diuretics to prevent hypokalemia while enhancing BP reduction 2
The 2024 ESC guidelines emphasize first-line therapy with ACE inhibitors/ARBs, CCBs, and thiazide diuretics 6, with amiloride reserved for resistant cases where additional agents are needed.