Optimizing Spironolactone Absorption
Take spironolactone with food to maximize absorption—this increases bioavailability by approximately 95% compared to fasting conditions. 1
Key Absorption Strategy
Take With Food (Most Important)
- Food dramatically enhances spironolactone absorption, increasing the area under the curve (AUC) by 95.4% for the parent drug 2
- Food also increases AUC of active metabolites by 21-45% 2
- The mechanism involves both increased absorption and decreased first-pass metabolism 3
- Canrenone (active metabolite) bioavailability is significantly enhanced when spironolactone is taken with meals 4
Establish Consistent Timing
- Patients should establish a routine pattern for taking spironolactone with regard to meals—either always with food or always without food to maintain consistent drug levels 1
- Single morning dosing maximizes compliance 5, 6
- The long half-life of spironolactone (1.4 hours for parent drug, 13.8-16.5 hours for active metabolites) supports once-daily dosing 1
Practical Dosing Recommendations
Standard Approach
- Administer as a single morning dose with breakfast to optimize both absorption and compliance 5, 6
- Starting dose is typically 25-100 mg once daily depending on indication 5
- For ascites in cirrhosis: begin with 100 mg daily 5
- For heart failure: begin with 25 mg daily 5
Formulation Considerations
- Micronized formulations improve oral absorption compared to standard preparations 3
- Tablet bioavailability is approximately 92-100% relative to solution formulations 7
- Peak plasma concentrations occur at 2.6 hours for spironolactone and 4.3 hours for canrenone 1
Important Caveats
Monitoring Requirements
- Check potassium and renal function before starting, at 1 and 4 weeks after initiation, and after any dose changes 5, 6
- If potassium rises >5.5 mmol/L, halve the dose; if ≥6.0 mmol/L, stop immediately 5, 6
- The absorption-enhancing effect of food means consistent timing with meals is critical to avoid unpredictable drug levels 1