Diuretics for Pets: What You Should Know

Diuretics, also called "water pills," are a class of medications that help rid the body of water and salt (sodium) through the urine. The kidneys put more sodium in the urine. In turn, this increased sodium helps to take water from the blood. Removing this excess water from the blood vessels reduces pressure on the walls of the arteries making it easier for the heart to pump.

Understand the difference between diuretics
There are three major categories of diuretics: thiazide diuretics, loop diuretics, and potassium sparing diuretics. Each of these diuretic medications works in a different area of the kidneys to produce the desired effect.
An example of a thiazide diuretic is hydrochlorothiazide (HCTZ). HCTZ removes excess fluid from the body and is used mainly to lower blood pressure. Furosemide is an example of a loop diuretic. Furosemide is more powerful than HCTZ and is often used in the treatment of congestive heart failure (CHF). Furosemide is also used in the treatment of pulmonary edema (fluid in the lungs), certain kidney diseases, ascites (fluid in the abdomen), and tissue edema (swelling). Spironolactone, an example of a potassium sparing diuretic and often used in combination with HCTZ, is used in the treatment of CHF and ascites.

Know the side effects of diuretics
Diuretics are generally safe, when used as directed. However, they do have some side effects. Side effects or signs of toxicity or overdose may include dehydration accompanied by excess thirst and decreased urination, or electrolyte imbalance accompanied by weakness, drowsiness, restlessness, dizziness, stumbling, and muscle pain or cramping. If any of these side effects occur, contact your veterinarian right away.
HCTZ and Furosemide should not be given to animals allergic to sulfa drugs such as SMZ/TMP, Albon, or Primor. Spironolactone should not be given to animals with Cushing's disease treated with mitotane (Lysodren), or animals that are being treated for Addison's disease.
Your pet needs to eat and drink well to reduce the risk of side effects. Furosemide should not be used in animals that don't produce urine, have progressive kidney disease, electrolyte imbalances, liver disease, diabetes mellitus, vomiting, or diarrhea. Diuretics should not be used in pregnant animals, or nursing animals. Your veterinarian should be consulted before giving your pet any other medications, including vitamins and supplements, since interactions may occur.