Effects of Furosemide in Dogs

Furosemide is a drug that, like all others, can only be prescribed by a vet. This professional is the only one qualified to decide whether it's suitable, the recommended dose, and the instructions for giving it.

So, even if we have furosemide at home, have used it before, and think it's what our dog needs, we should never give it on our own, since we could cause serious poisoning.

What Is Furosemide?

Furosemide is a diuretic drug, meaning it's used to eliminate fluids that have built up in excess in the body due to different causes. As with all medications, before using them we need to weigh the pros and cons of giving them, as well as consider possible side effects.

How Does Furosemide Work?

A fairly common example of furosemide use is pulmonary edema. This condition occurs when fluid builds up in these organs due to conditions such as heart disease.

By giving furosemide, the excess fluid is eliminated, and we'll notice that, within a short time, the dog will feel the urge to urinate and will do so abundantly. This improves its condition until the cause of the buildup is resolved. That said, we need to know diuretics may need to be used for extended periods, since the cause can be chronic.

Since we're eliminating fluids, good veterinary monitoring is needed so we don't run the opposite risk, meaning dehydration. In dogs with severe or acute conditions, fluid management, with intravenous fluid therapy and diuretics, needs to be done intensively, with the animal hospitalized at the vet clinic.

What Dose of Furosemide Does a Dog Need?

Managing the body's fluids is delicate. That's why dogs being given diuretics need to follow strict veterinary monitoring. This is because the drug is prescribed to help eliminate fluids, but these can build up in greater or lesser amounts, which is why the dose needs to be adjusted.

So, even if our dog has already been treated with furosemide before, we can't repeat the same treatment without the vet examining it and prescribing the right schedule for its current circumstances.

Dosing for any drug can range between a minimum and maximum dose, usually set per kg of weight per day. Depending on the disease being treated, the dog's condition, and its characteristics, the vet will choose the most suitable dose within that range.

What Happens If the Furosemide Dose Isn't Correct?

If a dog receives a lower amount of furosemide than it needs, the result will be that the fluid buildup will persist, meaning the symptoms will continue. In these cases, the vet will need to raise the dose, consider switching to another diuretic, or reconsider the diagnosis and treatment.

On the other hand, if the dose exceeds the recommended amount, we could even cause poisoning. Drugs have a safety margin, so slightly exceeding the maximum prescribed amount doesn't necessarily cause harm. But if, by accident, we greatly exceed the dose, the effects can be very negative.

Furosemide Overdose

If we give furosemide or any other diuretic on our own and the dose exceeds the maximum recommended, we could cause our dog moderate to severe poisoning, depending on the amount ingested and the animal's condition.

If an overdose occurs, we'll notice symptoms such as the following:

• Significant dehydration — if we pinch a fold of skin between our fingers and pull, it will take time to return to its position.
• Intense thirst.
• Greatly increased urine output.
• Apathy — the dog has no energy.
• In some cases, luckily less common, acute kidney failure can occur, putting the animal's life at risk.

What Do I Do If My Dog Has Taken a High Dose of Furosemide?

If we notice any of the poisoning symptoms described, we shouldn't hesitate to see the vet. We need to be aware that dehydration, if not corrected, can have fatal effects. This is especially important in animals that are already weakened, very old, or puppies, since they're more vulnerable.

Faced with any suspicion of improper furosemide intake, the only option is to contact the vet so they can examine our dog and put the appropriate treatment measures in place.

To avoid scares, we stress again that we should never give our dog any medication without a vet's prior prescription. In addition, we'll keep medications in places inaccessible to dogs, to prevent them from being able to swallow them.

Bibliography: Nelson & Couto (2010, 4th edition): Medicina interna en pequeños animales, Barcelona: Elsevier.