Pet Medication 101: Furosemide

Furosemide for dogs and cats

It’s important to understand a medication’s uses and side effects before giving it to your pet. This medication info sheet is meant to give you a good understanding of what furosemide (Lasix) is used for, how it works, and potential side effects in cats and dogs. Always consult a veterinarian before giving your pet any medication.

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1. Drug Name:

Furosemide

2. Brand Names:

Lasix, Salix, Disal

3. How Dispensed:

Prescription-only

4. Forms:

Veterinary labeled products: 12.5mg and 50mg tablets, 10mg/mL oral solution, 50mg/mL injectable solution

Human labeled products: 20, 40, and 80 mg oral tablets, 10mg/mL and 40mg/5mL oral solution, 10mg/mL injectable solution

5. Drug Type/Class:

Loop diuretic

6. Uses in Dogs and Cats:

Furosemide is used as a diuretic, which removes fluid and sodium from the body. It is used in dogs and cats to treat congestive heart failure, pulmonary edema (excess fluid in the lungs), hypercalcuric nephropathy (high calcium levels damaging the kidneys), uremia (high levels of urea and other waste products in the blood damaging the kidneys), to lower potassium levels and occasionally as an antihypertensive (blood pressure) agent.

Furosemide is the most frequently used drug for treating both left heart failure (pulmonary edema in dogs and pulmonary edema/pleural effusion in cats) and right heart failure (ascites in dogs and cats and subcutaneous edema in cattle and horses). Furosemide also often reduces cough in dogs with chronic bronchitis.

7. How it Works:

Furosemide acts on a portion of the kidney to reduce the absorption of electrolytes and increases urinary excretion of fluid, sodium, and other electrolytes.

8. Side Effects and/or Signs of Overdose:

Side effects of diuretics include increased thirst and urination and gastrointestinal irritation. Abnormalities to fluid and electrolyte levels may occur so patients should be monitored closely for hydration status and electrolyte imbalances. It can cause severe dehydration if the dosage is very high or the patient is not drinking which can lead to weakness and collapse.

Furosemide commonly increases kidney values, creatinine and BUN, due to the loss of fluid. More commonly in cats than dogs, furosemide can lead to ototoxicity, when a medication has affected the ear causing hearing or balance problems.

An overdosage may result in convulsions, abnormal/wobbly gait, paralysis, and collapse.

9. Drug Interactions:

  • Ace inhibitors: commonly used together but may increase risk of hypotension (low blood pressure)
  • Furosemide usage can alter insulin requirements in diabetic patients
  • Aminoglycoside antibiotics (such as gentamicin or amikacin) may increase the risk of ototoxicity
  • Amphotericin B
  • Digoxin
  • Corticosteroids
  • Muscle relaxants
  • Probenecid
  • Salicylates
  • Succinylcholine
  • Theophylline

10. Cautionary Statements:

  • Furosemide can produce clinically significant dehydration and electrolyte imbalances
  • Frequent laboratory monitoring is needed for patients who are prescribed furosemide as it commonly increases kidney values and causes electrolyte abnormalities
  • Ensure patient is adequately hydrated before administration; should not be administered to a dehydrated patient
  • Contraindicated during pregnancy
  • Diabetes mellitus may be exacerbated by the use of furosemide
  • Use with caution in patients with liver failure and anuria (failure for the kidneys to produce urine)

Read more:

Can cats develop heart disease?

Kidney Failure in Cats

Heart Murmurs in Dogs

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