Prednisone is a corticosteriod used to treat a wide range of chronic problems, such as asthma, lupus, arthritis, cancer, allergies and autoimmune disease. Since it is a powerful hormone, prednisone can give your dog immediate relief from uncomfortable symptoms. On the flip side, however, its powerful effect on the body can cause serious problems.

Length of Use

The type of side effects or problems caused by prednisone depend greatly on how long your dog takes the medication. When used only for a short time, the side effects generally are limited and temporary. If given over a long period of time, however, prednisone can cause permanent, serious health problems. If your veterinarian is recommending long-term treatment with prednisone, be sure to discuss whether the benefits outweigh the risks. Even though there are some serious potential side effects, for some diseases prednisone is the medication with the lowest risk.

Short-Term Side Effects

When used for short-term treatment, often for severe allergies or skin problems, prednisone can cause excessive thirst and frequent urination. These symptoms should abate as soon as the treatment is over, but in the meanwhile it may be necessary to let your dog outside frequently to prevent accidents. In some dogs prednisone can cause vomiting, diarrhea and lethargy. Contact your veterinarian if your dog has any of these side effects to determine whether to continue treatment.

Diabetes, Cushing’s and Addison’s Disease

Prednisone changes your dog’s body in many ways when taken for long periods of time. For example, high doses can raise your dog’s blood sugar level, eventually leading to diabetes. The constant high levels of corticosteroids can alter your dog’s hormones and metabolism, which can result in either Cushing’s or Addison’s disease. Signs of these illnesses include dry skin, a pot belly, hair loss, oily skin and weight loss.

Suppressed Immune System

Corticosteroids such as prednisone work by suppressing your dog’s immune system. This can stop autoimmune diseases or allergies in their tracks, but it also leaves your dog vulnerable to illness and infection. For example, a small cut that would normally heal without incident can become infected because your dog’s body cannot react to protect him against bacteria in the wound. Keep a close eye on your dog while he is taking prednisone and contact your veterinarian immediately if he shows any sign of infection or illness.

Other Side Effects

Long-term use of prednisone can lead to stomach ulcers, changes in behavior, stunted growth, kidney disease, colitis and fluid retention. Stopping the medication suddenly can lead to serious problems, such as a heart attack. Your dog should be tapered off of prednisone.