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Drugs Used to Treat Kidney and Urinary Tract Disorders

By

Patricia M. Dowling

, DVM, MSc, DACVIM, DACVCP, Veterinary Clinical Pharmacology, Western College of Veterinary Medicine, University of Saskatchewan

Last full review/revision Jul 2011
Topic Resources

Drugs used to treat urinary disorders include antibiotics and antifungal medications for infections, diuretics for kidney failure, and a variety of other drugs for several other disorders.

Antibiotics

Antibiotic drugs are the basis of urinary tract infection treatment. Antibiotic treatment involves determining the type of bacteria present and choosing the appropriate drug. There are many types of antibiotics; your veterinarian will prescribe one that is excreted in an active form in the urine and is known to be effective against the particular bacteria present ().

Many animals with recurrent urinary tract infections are treated with repeated courses of antibiotics. However, if the underlying cause of the infection is not found, the repeated courses of antibiotics can do more harm than good. Inappropriate treatment with the wrong antibiotic can cause bacteria to become resistant (see Guidelines for the Use of Antibiotic Drugs). Chronic urinary tract infections from highly resistant bacteria are very hard to treat.

If episodes occur more than once or twice yearly, and the causes of the urinary tract infections cannot be found or corrected, longterm low-dose treatment with oral antibiotics may be necessary to prevent new episodes.

Antifungal Drugs

Although uncommon, fungal urinary tract infections occur in dogs and cats. Treatment involves removing any predisposing factors (excessive corticosteroids, urinary catheters) and giving antifungal drugs, with or without urinary alkalinization (see Controlling Urine pH).

Controlling Urine pH

pH is the measure of how acidic or alkaline (basic) a substance is. Urine with abnormally high or low pH can contribute to the formation of certain types of kidney or bladder stones. In dogs, urine pH should be between 7 and 7.5. In cats, it should be between 6.3 and 6.6. Potassium citrate can be used to raise the pH, making it more alkaline (basic). Ammonium chloride or DL‑methionine can be used to lower the pH, making it more acidic.

Cystine-binding Agents

Cystinuria, with the formation of cystine kidney stones, is caused by an inherited disorder. Cystine kidney stones are dissolved with changes in the diet, urinary alkalinization or neutralization, and the use of cystine-binding agents. Once stones are dissolved, changes in the diet can help prevent them from coming back.

Diuretics

Diuretics are used to remove excess water from animals with swelling or volume overload, such as that which occurs with kidney failure. There are several classes of diuretics, grouped by the way they act in the body (see Table: Diuretics*). Loop diuretics are named because of their effect on the ascending loop of Henle in the kidney. Carbonic anyhdrase inhibitors work by decreasing the formation of carbonic acid, making more sodium bicarbonate, which takes water with it when it is excreted. Carbonic anhydrase inhibitors also enhance potassium excretion. Thiazide diuretics are infrequently used, but they may be given to animals that cannot tolerate the more potent loop diuretics. Thiazides can be combined with loop or potassium-sparing diuretics. They may also be used to treat diabetes insipidus, which affects the kidneys. Potassium-sparing diuretics do not cause the loss of potassium, which is beneficial in some conditions in which potassium levels may be low. These are usually used in combination with other diuretics, rather than alone. Osmotic diuretics keep water from being reabsorbed in the kidneys.

Table
icon

Diuretics*

Drug

Chlorothiazide

Dimethyl sulfoxide

Furosemide

Hydrochlorothiazide

Mannitol

Spironolactone

*Many of the drugs listed are not directly approved by the FDA for treatment in all species. Veterinarians decide what drug and dosage to use for an animal based on their experience, published reports, and continuing education.

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