Spironolactone

What is sprironolactone?

Spironolactone (brand names: Aldactone®, Prilactone®, Tempora®, CaroSpir®) is a potassium-sparing diuretic used as an adjunctive therapy to treat congestive heart failure. It has also been used to treat fluid accumulation in the abdomen and may be effective for treating kidney disease or high blood pressure. 

Its use in cats and dogs to treat heart failure and other cardiovascular conditions is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label. 

How is spironolactone given? 

• Spironolactone is given by mouth in the form of a tablet. It may also be compounded into a liquid form; measure liquid forms carefully.
• It can be given with or without food.
• If your pet vomits when dosed on an empty stomach, give future doses with food.
• Always allow your pet access to clean and plentiful water while giving this medication.
• Because this medication causes more frequent urination, do not give the last dose close to bedtime, to reduce the need for your pet to urinate at night. 

This medication should take effect within 1 to 2 hours; however, effects may not be noted outwardly, and laboratory tests may be needed to evaluate this medication’s effectiveness.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once. 

Are there any potential side effects? 

Spironolactone may cause the following side effects:

• Increased drinking and urinating
• Mild decreases in energy
• Mild electrolyte imbalances
• Vomiting and diarrhea

Serious adverse reactions may occur. If any of the following signs develop, stop giving spironolactone and contact your veterinarian immediately:

• Facial itchiness
• Rash/skin sores
• Persistent vomiting or diarrhea
• Severe tiredness
• Fast heartbeat
• Difficulty walking
• Collapse
• Loss of balance
• Lack of appetite
• Lack of urinating

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE spironolactone in pets that:

• Are allergic to it
• Have elevated potassium levels
• Have Addison’s disease
• Have acute kidney failure
• Have significant kidney disease
• Are not urinating
• May be used for breeding

USE WITH CAUTION in pets that:

• Have liver disease
• Are pregnant or lactating
• Have uncontrolled diabetes
• Have other conditions that cause blood electrolyte imbalances

Are there any drug interactions I should be aware of?

Several medications should be used with caution when given with spironolactone, including:

• Digoxin
• Mitotane
• Neuromuscular blockers
• Other potassium-sparing diuretics
• Potassium supplements
• Salicylates

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is any monitoring needed with this medication?

• Blood electrolytes and kidney values (BUN, creatinine) will be measured before your pet starts this medication, 1-2 weeks after starting, and then every 2 months thereafter.
• Blood pressure, weight, and hydration may also need to be monitored.
• Your veterinarian may monitor your pet to be sure that the medication is working by watching for swelling.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store spironolactone?

• Store the tablets at room temperature (68°F to 72°F or 20°C to 22°C) and protect from light and moisture.
• Store compounded liquids according to the label.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.