What to Know About Furosemide for Dogs

Medically Reviewed by Amy Flowers, DVM on December 09, 2021
3 min read

Your veterinarian uses furosemide to treat dogs with some critical conditions. Furosemide is a diuretic (a drug that increases urine production). It stimulates the kidneys to produce more urine and remove excess fluid from the body. This relieves the work your dog's heart has to do. It also relieves fluid collection in the lungs that can be life-threatening. Furosemide is also used to treat ascites (fluid collection in the abdomen).

Furosemide is classified as a loop diuretic. That means it acts on a specific part of your dog's kidneys known as the loops of Henle. Here, furosemide prevents sodium and water from being reabsorbed, so that they're excreted in the urine.

With increasing age, your dog may develop a condition known as degenerative mitral valve disease (DMVD). It is common in dogs and often causes heart failure. You may notice your dog gets tired and breathless easily.

The American College of Veterinary Internal Medicine (ACVIM) recommends furosemide for the treatment of heart failure in dogs. Other recommended drugs are beta blockers, pimobendan, digoxin, enalapril, and spironolactone. Your veterinarian will prescribe one or more of these drugs, depending on the severity of the heart failure. 

When your dog has heart failure, fluid may collect in their lungs. This condition is called pulmonary edema and is extremely dangerous. Furosemide can be life-saving by removing fluid from the lungs. Your veterinarian will probably give the drug by injection for rapid action.

Signs of heart failure in dogs include:

If your dog has cancer, your veterinarian may prescribe cyclophosphamide, an anticancer drug. One of its side effects is hemorrhagic cystitis, a severe inflammation of the urinary bladder. Furosemide can prevent this side effect. Furosemide is also used to treat hypertension (high blood pressure) and hyperkalemia (high levels of potassium is the blood).

Furosemide is usually given by mouth. The drug is available as a tablet and as a liquid. When given by mouth, it is about 77% absorbed. 

After your dog takes furosemide by mouth, their urine output increases in 1 to 2 hours. The action of furosemide lasts for 6 hours. If it is given by IV injection, its action starts in 5 minutes. The urine output returns to baseline in 4 hours.

The usual dose of furosemide for healthy dogs is 1 to 5 milligrams per kilogram of your dog's weight, two or three times a day. If your dog has heart failure, the blood supply to their kidneys may be reduced. If this is the case, not enough furosemide may reach the kidneys. Your veterinarian may decide to give higher doses. 

If your dog has pulmonary edema, your veterinarian will give furosemide by intravenous injection. Injections are a sure way to get the drug into your dog's body, compared to tablets (which your dog may spit or vomit). High doses are used in this life-threatening condition.

Furosemide is a diuretic drug and acts on the kidneys. The side effects are similar to other diuretic drugs:

  • Hypokalemia, low potassium blood levels, which can affect nerve, muscle, and heart function
  • Hyponatremia, low sodium blood levels, which can cause lethargy, fits, and brain damage
  • Acid-base abnormalities, like metabolic alkalosis, which causes lethargy, unconsciousness, or fits
  • Dehydration
  • Azotemia, an increase of blood urea and creatinine levels
  • Ototoxicity, damage to the hearing of your dog, especially if high doses are used. Other diuretic drugs do not have these side effects.

If your dog is on furosemide for a long time, they may become resistant to its effect. Your veterinarian may need to prescribe higher doses. The adverse effects of this drug are sometimes worse if your dog is also getting digoxin for heart failure.

For long-term treatment, your veterinarian will give you a liquid preparation or tablets. These are the best options for treatment at home. 

Your dog may not be cooperative about taking drugs by mouth. You can try other methods like films that dissolve in the mouth. Intramuscular (IM) and subcutaneous (SC, under the skin) injections can also be used. 

In urgent situations, your veterinarian will give furosemide by intravenous (IV) injection, or as a continuous IV infusion.