Furosemide (Lasix) & Spironolactone
Together for Dogs with Heart Disease
A complementary diuretic combination. Furosemide is a powerful loop diuretic that depletes potassium, while spironolactone is a mild potassium-sparing diuretic that helps balance this effect.
Why are these prescribed together?
Furosemide is the most effective diuretic for removing fluid from the lungs but it wastes potassium and magnesium. Spironolactone provides additional mild diuretic effect while retaining potassium, partially counteracting furosemide's electrolyte imbalance. Spironolactone also has anti-fibrotic effects on the heart.
How they interact
Complementary potassium effects: furosemide depletes K+, spironolactone retains K+. Together, potassium levels are more stable than with furosemide alone. However, potassium levels should still be monitored.
Dosing and timing tips
Furosemide can be given 1-3 times daily depending on severity. Spironolactone typically once daily with food. Space furosemide doses evenly through the day.
Monitoring needed
Electrolytes (especially potassium - can go too high or too low). Kidney values. Body weight. Hydration status.
Important warnings
Never add potassium supplements without bloodwork - the spironolactone may already be keeping potassium adequate
Adjust furosemide dose only as directed by your vet
Watch for changes in water intake and urination patterns
Used for these conditions
Learn about each medication
Other combinations with these drugs
Cardiac protocols stack up over time. These pages cover the other combinations your dog may end up on.
Furosemide (Lasix) & Benazepril
A foundational combination in heart failure management. Furosemide removes fluid while benazepril reduces the hormonal response that causes fluid retention.
Furosemide (Lasix) & Enalapril
Same rationale as furosemide + benazepril. Enalapril blocks the hormonal response that causes fluid retention while furosemide directly removes excess fluid.
Pimobendan (Vetmedin) & Furosemide (Lasix)
The most common combination for dogs in congestive heart failure. Pimobendan strengthens the heart while furosemide removes excess fluid from the lungs.
Pimobendan + Furosemide & Benazepril
The 'triple therapy' - the standard of care for dogs in congestive heart failure. Most cardiac dogs in Stage C will be on all three of these medications.
Important:Never start, stop, or adjust your dog's medication without consulting your veterinarian. The dosages and protocols described here are general references - your vet will determine the right approach for your dog based on their individual condition, weight, and overall health.