Furosemide (Lasix®)

Furosemide (Lasix®)


Furosemide is a medication that is commonly prescribed for heart disease in dogs and cats.  It is infrequently used to treat other medical conditions, including high blood pressure or, rarely, certain kidney and urinary disorders.

Furosemide is in a class of medications called diuretics.  Medications in this class work by causing increased urine production.

In the treatment of heart disease, furosemide works by causing excess fluid that has built up in the lungs to be excreted as urine. This leads to reduced coughing (cats, dogs) and decreased respiratory effort in animals that suffer from congestive heart failure.


Furosemide is readily available for oral administration in tablet or liquid suspension form. Special pharmacies may be able to produce palatable formulations of the medication to ease administration to pets.

Injectable furosemide is frequently used by veterinarians.

Side Effects

Urine output is expected to increase when furosemide is administered.  This is the desired effect of the medication, but it may result in house soiling (cats, dogs) or, in dogs, frequent requests for access to outdoor areas.

Pets that take furosemide may experience gastrointestinal upset (vomiting, diarrhea, or decreased appetite), hearing loss, dehydration, or electrolyte (blood salt) imbalances. Signs of dehydration and electrolyte imbalances include lethargy, excessive thirst, restlessness, and low urine output.

Contact your veterinarian immediately if you suspect your pet is suffering side effects from furosemide.

Furosemide must be used cautiously in pets with kidney disease.


Most patients take furosemide for long periods of time.  For pets that take the medication for congestive heart failure, improvement in coughing (cats, dogs) and respiratory effort should be monitored.

Patients that take furosemide should receive regular veterinary checkups and undergo periodic blood tests to monitor the function of the liver and kidneys.

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The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.