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Prednisone for Veterinary Use
by Barbara Forney, VMD
Prednisone is a synthetic corticosteroid used for many conditions in both human and veterinary medicine. Its anti-inflammatory activity is approximately four times that of hydrocortisone. Corticosteroids are extremely effective anti-inflammatory drugs because they affect the inflammatory process at so many different levels. Prednisone is rapidly converted to prednisolone in the liver and, in most instances, these drugs are considered to be roughly equivalent. Corticosteroids have strong beneficial effects but a definite potential to cause negative side-effects if abused. Prednisone may be given by injectionorally or topically.
Dogs and Cats
Prednisone is used for a wide variety of conditions in both dogs and cats. It may be used in emergency situations including anaphylactic reactions, spinal cord trauma and many forms of shock. It is used to manage and treat immune mediated disease such as immune-mediated hemolytic anemia or thrombocytopenia, many CNS disorders, some neoplasia, dermatologic diseases, allergic reactions such as asthma, hives and itching, inflammatory orthopedic diseases, endocrine disorders including Addison's Disease, respiratory disease with an inflammatory component, inflammatory bowel diseases, and many other conditions.
Cats may require higher doses than dogs in order to achieve clinical response but they are less likely to develop adverse side effects.
Prednisone is given systemically to decrease inflammatory and immune responses. For years it was used orally to treat Chronic Obstructive Pulmonary Disease (COPD) and other allergic or immune mediated disorders. Recent work has demonstrated that horses do not absorb oral prednisone although they do absorb oral prednisolone. Other corticosteroids are preferred for intra-articular use.
Prednisone Side Effects
- Systemic side effects of corticosteroids generally are dependent on dose and duration of treatment. Short-term use of prednisone is unlikely to cause adverse effects. Adverse effects are more common in animals on immunosuppressive doses.
Side effects seen in dogs include polyuria, polydipsia, polyphagia, poor haircoat, GI disturbance, diarrhea, vomiting, weight gain, GI ulceration, pancreatitis, lipidemia, elevated liver enzymes, diabetes mellitus, muscle wasting and possible behavioral changes. Polyuria, polydipsia, polyphagia may be seen in dogs even on short-term therapy.
Although cats are less likely to develop side effects than dogs, occasionally polyuria, polydipsia, polyphagia, weight gain, GI disturbances and behavioral changes occur.
- Corticosteroids can cause or worsen gastric ulcers.
- Chronic or inappropriate use of corticosteroids, including prednisone, can cause life-threatening hormonal and metabolic changes.
- Adverse effects due to corticosteroid treatment usually occur with long-term administration of the drug, especially when high doses are used. Alternate day therapy with short-acting preparations is preferred. Animals that have received long-term therapy should be withdrawn slowly by tapering the dosage and prolonging the interval between doses.
- Corticosteroids suppress immune response. Animals receiving systemic corticosteroids may be more susceptible to bacterial or viral infections. Systemic corticosteroids can mask signs of infection, such as an elevated temperature.
- Systemic corticosteroids are contraindicated in patients with systemic fungal infections. The treatment of Addison's Disease may be considered an exception.
- Prednisone must be converted to prednisolone in the liver. Animals in hepatic failure should receive prednisolone rather than prednisone.
- Corticosteroids should be avoided or used very carefully in young animals both because of immune suppression and the risk of GI ulcers.
- Corticosteroids have been implicated as a cause of laminitis in horses and ponies. Some corticosteroids are thought to be more likely to
- cause laminitis than others and prednisone historically has not been considered to be in the higher-risk category. Pony breeds may be more susceptible to developing laminitis than horses.
- Although corticosteroids may be used in healthy older horses, they should not be used in horses with pituitary pars intermedia
dysfunction. These horses already may have high levels of natural corticosteroids and are prone to laminitis and suppressed immune function.
- Corticosteroids should be avoided during pregnancy and lactation unless the benefits outweigh the risks. Large doses in early pregnancy may be teratogenic. Corticosteroids can induce labor and have been used to terminate pregnancy in bitches.
- When amphotericin B or diuretics such as furosemide are given with corticosteroids, there is an increased risk of electrolyte imbalances due to calcium and potassium losses.
- Digitalis and potassium levels should be monitored closely in animals taking prednisone.
- Corticosteroids may increase insulin requirements. Estrogen may potentiate the effects of corticosteroids.
- Drugs that may cause drug interactions with prednisone include salicylate, phenytoin, phenobarbital, rifampin, cyclosporin, erythromycin, mitotane and anticholinesterase drugs such as neostigmine and pyridostigmine.
- The immune response to vaccination may be reduced when corticosteroids are given at the same time.
- The risk of GI ulcers may be increased if corticosteroids and other drugs prone to causing ulcers such as nonsteroidal anti-inflammatory drugs are given at the same time.
Short-term administration of even large doses is unlikely to cause serious harmful systemic effects due to adrenal suppression. Problems associated with long-term administration of prednisone relate to suppression of normal adrenal function, iatrogenic Cushing's Disease and metabolic crisis due to abrupt withdrawal.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
You can purchase books by Dr. Forney at www.exclusivelyequine.com
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