Spironolactone. III. Canrenone--maximum and minimum steady-state plasma levels

Area of Science:

• Pharmacokinetics
• Clinical Pharmacology

Background:

• Spironolactone is a widely used medication.
• Understanding its active metabolite, canrenone, pharmacokinetics is crucial for optimizing therapy.
• Repeated dosing regimens can influence drug accumulation and elimination.

Purpose of the Study:

• To compare steady-state plasma levels and post-steady-state half-life of canrenone.
• To evaluate two different spironolactone dosing regimens: 200 mg once daily versus 50 mg four times daily.

Main Methods:

• 23 healthy men received repeated doses of spironolactone for 15 days.
• Plasma levels of canrenone were measured to determine steady-state concentrations.
• Post-steady-state half-life was calculated for each dosing regimen.

Main Results:

• Steady-state canrenone levels were achieved within 3-4 days for both regimens.
• Once-daily dosing resulted in lower minimum steady-state levels (approx. 100 ng/ml) compared to multiple daily doses (approx. 200 ng/ml).
• The post-steady-state half-life of canrenone was significantly longer with once-daily dosing (19.2 hr) than with multiple daily doses (12.5 hr).

Conclusions:

• Dosing frequency significantly impacts canrenone's pharmacokinetic profile.
• Once-daily spironolactone leads to a longer canrenone half-life, potentially influencing its therapeutic effect and duration.
• These findings are relevant for optimizing spironolactone dosage regimens.