Furosemide (Salix, Lasix) for Dogs

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What Is Furosemide Used for in Dogs?

Furosemide is a diuretic (water pill) used to relieve edema, which is swelling caused by fluid trapped in the body’s tissues.

Edema can be caused by heart disease or heart failure, kidney failure, high blood calcium, high blood potassium, and/or other non-inflammatory causes of edema.

Furosemide is available under the brand names Disal and Salix (FDA-approved in animals) and Lasix (only FDA-approved for humans).

Furosemide may be given by injection by your veterinarian in an emergency setting. It’s also available in oral tablet formulation.  

Generally, furosemide is not given alone but is used in conjunction with other medications depending on the underlying cause of the edema.

Compounded Furosemide for Dogs

In certain circumstances, your vet may recommend a compounded formulation of a medication.

Compounded medications are prescribed if there’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if your pet has trouble taking pills in capsule form, the dosage strength is not commercially available, or the pet is allergic to an ingredient in the FDA-approved medication.

Compounded medications are not FDA-approved. They’re created by either a veterinarian or a licensed pharmacist on an individual basis to best suit a patient’s particular needs.

Your veterinarian will determine whether a compounded medication is right for your pet.

Furosemide for Dogs Considerations

Furosemide should not be used in pets that are incapable of producing urine, have low calcium levels, or have an allergy to furosemide or sulfa drugs.

Furosemide should be used with caution in pets with electrolyte abnormalities, dehydration, kidney disease, liver disease, or diabetes.

How Furosemide Works in Dogs

Furosemide works on the kidneys by changing the balance of electrolytes filtered into the urine. This causes excess water in the body to shift from the tissues and into the urine so edema (swelling) in the body can subside.

Furosemide for Dogs Directions

Follow the directions on the drug label or as provided by your veterinarian. Your veterinarian may need to adjust the dosage based on how your pet responds to the medication.

Make sure that your pet has access to plenty of fresh water while on this medication.

Missed a Dose?

Speak with your veterinarian about what to do if you forget to give a dose of furosemide.

Generally, they may instruct you to give it when you remember, or, if it is almost time for your pet’s next dose, to skip the missed dose and resume your normal dosing schedule.

Do not give extra or double doses.

Possible Side Effects of Furosemide for Dogs

Side effects are uncommon with furosemide, although increased thirst and urination can be expected in dogs.

The side effects listed below may occur and are related to the fluid and electrolyte changes caused by furosemide:

• Dehydration

• Abnormal urine production

• Electrolyte imbalances

• Vomiting and/or diarrhea

• Weakness

• Increased heart rate

• Depression or restlessness

• Damage to the ear (decreasing the ears’ ability to hear and/or balance)

Human Side Effects

Furosemide is also a prescription medication for humans, frequently with dosages different from those prescribed for your pet by a veterinarian.

Due to possible side effects, humans should never use medicine dispensed for their pets and pets should not be given any medicine dispensed for a human’s use.

If you accidentally ingest a pet medication, call your physician or the national Poison Control Center hotline at 800-222-1222.

Monitoring Your Pet

Animals on furosemide should receive periodic blood work to monitor kidney and electrolyte levels during early therapy and periodically thereafter.

Your veterinarian may also recommend monitoring your pet's weight, blood pressure, or other testing based on your pet’s individual needs.

When To Call Your Vet

Call your veterinarian if any of the following apply:

• Severe side effects are seen (see above)

• Your pet’s condition worsens or does not improve with treatment

• You see or suspect an overdose

• You have additional questions or concerns about the use of furosemide

Furosemide Overdose Concerns in Dogs

One-time overdoses are likely to cause side effects related to fluid and electrolyte imbalances that are listed above.

Toxic doses can lead to convulsions, impaired coordination, paralysis, and collapse.

If you suspect an overdose, immediately contact your veterinarian or an animal poison control center. Consultation fees often apply.

• Pet Poison Helpline 855-764-7661

• ASPCA Animal Poison Control 888-426-4435

How To Store Furosemide for Dogs

Keep the following storage tips in mind:

• Always confirm storage requirements by reading the prescription label.

• Furosemide should be stored at controlled room temperatures of 68–77 F (20–25 C).

• Keep the container tightly closed to protect from moisture and light.

• Compounded medications should be stored according to the compounding pharmacy’s label.

• Keep out of reach of children and pets.