Prescription pillsWhat is Lasix?

Lasix is in the family of medications most commonly known as diuretics (water pill). It helps the body get rid of water by increasing the kidneys production of urine.


  • Most important medication in the treatment of acute and chronic congestive heart failure
  • Edema (fluid accumulations) for other reasons other than heart failure
  • Some forms of acute kidney failure
  • Elevated blood calcium levels
  • Used at low dosages in some dogs with chronic bronchitis

Adverse Effects

[please contact CVCA should any of these symptoms be noted]

  • Increased thirst and urination (please contact us if this seems excessive)
  • Can result in dehydration in patients not drinking well, or with other diseases that could cause excessive fluid loss (kidney disease, vomiting/diarrhea)
  • Causes loss of certain electrolytes in the urine (calcium, sodium, potassium, magnesium). In patients not eating well, this could result in weakness, worsened appetite, and an increased risk for arrhythmias
  • Rapid high dose IV injections convey a low risk for hearing loss
  • Potential to increase blood sugar levels, altering the insulin need in diabetics
  • Could result in low blood pressure and weakness if used in patients with pericardial effusion


Client Information

  • Can be given with or without food
  • Almost never used as a sole medication in the treatment of congestive heart disease
  • Can be given in pill form, liquid or made into chewable treats
  • Do not stop or lower the dose without the approval of a veterinarian
  • Monitoring of kidney values and electrolytes through blood work should be done after starting or increasing the dose, and at least every 6 months thereafter
  • Often used in combination with an ACE inhibitor and/or spironolactone in veterinary medicine, decreasing the risk for low potassium
  • Salix is the preferential formulation of injectable lasix for patients receiving chronic at home SQ injections

Interaction with Other Drugs

  • Low blood pressure possible when com- bined with drugs that result in vasodilation (ACEi, amlodipine, diltiazem)
  • Concurrent use with certain antibiotics could increase risk for hearing loss (gentamicin, amikacin)
  • Increases blood levels of aspirin, theophylline
  • The doctors at CVCA have taken this into account, however, please feel free to contact CVCA regarding any concurrent medications your pet may be prescribed

Standard Dosage Forms

Lasix Oral Tablets – 12.5mg and 50mg (Veterinary Only), 20mg, 40mg, 80mg

Lasix Oral Solution – 10mg/ml


(Lasix, Furosemide, Salix)

Drug Handouts