Lasix Side Effects in Dogs

Lasix side effects in dogs are usually mild, but there are a few instances in which side effects can be serious. Let’s learn what Lasix does for your dog and if there are circumstances in which its use is not recommended, as well as examining the mild and potentially serious side effects of this medication so you'll know what to look out for if your pet ever takes this medication.

How Lasix May Help Your Dog

Lasix is a brand name medication that is also sold under the generic name furosemide. It is a diuretic, which means it helps remove water from your dog’s body by increasing his urinary output. Lasix increases urinary output by working on a specific part of the canine kidney called Henle’s loop. The medication stops the kidney from absorbing chloride, potassium, sodium and water, which increases the dog’s urinary output.

Diuretic drugs can be helpful in treating the following medical conditions:

  • congestive heart failure
  • edema
  • false pregnancy
  • high blood pressure
  • high levels of blood calcium and potassium 
  • kidney failure

Canine Side Effects from Lasix

Diuretic drugs have certain side effects that are inherent in the way they work on a dog’s body. These include increased thirst and more frequent urination. Other mild side effects can include:

  • blurred vision
  • constipation
  • diarrhea
  • dizziness
  • stomach pain

More significant side effects can include:

  • appetite loss
  • bleeding
  • dark urine
  • drowsiness
  • dry mouth
  • fever
  • irregular heartbeat
  • jaundice
  • lack of urination
  • lethargy
  • muscle pain
  • nausea
  • restlessness
  • vomiting
  • weakness

Weakness and lethargy are two side effects that require immediate veterinary notification. If you notice these symptoms in your dog, his blood potassium levels may have dropped below normal levels and need adjusting.

In certain instances, your dog may have an allergy to Lasix. Stop giving him Lasix and contact your veterinarian's office for further instructions if your dog shows any of these symptoms:

  • breathing problems
  • facial swelling
  • hives
  • swelling of the lips, throat or tongue

Although Lasix is frequently prescribed for canine heart failure patients, its use over time can create problems with vasodilating cardiac medications, such as benazepril, enalapril and lisinopril. In such cases, your veterinarian will need to control your dog’s kidney and electrolyte balance before adding the vasodilating medication to your pet’s care regimen.

Dogs that are eating prescription diets for heart or kidney disease may lose water-soluble vitamins from taking Lasix. However, most commercially available prescription diets have been formulated to compensate for these losses. If your dog will not eat a prescription diet, he may require vitamin supplements from your veterinarian.

Monitor your dog’s sun exposure while he’s taking Lasix because the medication can make his skin more prone to sunburn. If sunburn becomes a problem for your pet, apply sunscreen before allowing him outdoors and provide ample shaded resting spots for him in your yard.

Situations in Which Lasix Use May Not Be Recommended

In addition to the side effects outlined above, there are other circumstances under which Lasix use is not recommended. It can react with certain types of medications, such as aspirin, blood pressure medication, certain antibiotics, corticosteroids, digitalis and theophylline, so its use in dogs that take these medications needs to be monitored closely.

Lasix use may exacerbate other medical conditions, such as

  • calcium oxalate bladder stones
  • diabetes
  • liver disease
  • kidney disease

so monitor your dog’s condtion carefully to ensure his health isn’t compromised by taking Lasix.