The body's immune system kills infectious agents such as bacteria or viruses after they enter the body. Sometimes the immune system becomes overzealous and also causes damage to the body. Immunosuppressant drugs block or inhibit the immune system. Some immunosuppressants make infection more likely, however immunosuppressants are useful when the immune system is causing harm to the body.
Immunosuppressant Use in Dogs
Immunosuppressants cause a number of serious side effects in dogs. Their use should be prescribed by and closely supervised by a veterinarian. Immunosuppressants treat autoimmune disease, when the immune system is overactive and attacks the body, and when deposits from immune system activity become lodged in tissue. In dogs, the immune system sometimes attacks the blood cells, causing anemia; the lining of joints, causing arthritis; the skin, causing itchiness; or a multitude of tissues at once, as in lupus. Clumped materials from immune system activity sometimes become lodged in the kidneys, causing kidney disease. Veterinarians also use immunosuppressants to treat some types of cancer, in particular cancer involving the immune system.
Steroids used in relatively high doses suppress the immune system. Predisone and prednisolone are commonly used for long-term applications. Dexamethasone, more potent than prednisone, is used only briefly. Steroids used as immunosuppressants can cause side effects such as liver disease, stomach ulcers, skin disease, hair loss and diabetes. Steroids are usually prescribed in diminishing doses to avoid these side effects.
Veterinarians prescribe cyclosporin A, also called cyclosporine, a product of certain fungi, as a selective immunosuppressant which can reduce immune system activity without some of the negative side effects of steroids. Skin allergies respond well to cyclosporine use, and it has been used following bone marrow and kidney transplants to prevent organ rejection as well.
Other immunosuppressants used in dogs include azathioprine, cyclophosphamide, chlorambucil, gold salts, sulfones, tetracycline with niacinimide and pentoxifylline. Veterinarians prescribe these drugs for a variety of problems including lupus and other skin diseases caused by damage from the immune system.