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Dexamethasone-21-isonicotinate is an esterified form of dexamethasone that is approved and marketed for horses. Work in laboratory animals has shown it to be more powerful and longer acting than the parent compound. Multiple laboratory tests on different species have shown significantly increased anti-inflammatory activity and duration of response, without increases in catabolic effects or adverse effects on electrolyte metabolism.
Corticosteroids are powerful drugs and the chronic or
inappropriate use of these drugs can cause life threatening hormonal and
metabolic changes. A major goal in the research and development of new
corticosteroids has been to develop drugs with fewer side effects and
less crossover effect on electrolyte metabolism.
In the horse, corticosteroids are given systemically to decrease inflammatory and immune responses. They are used systemically in high doses in emergencies for anaphylactic reactions, spinal chord trauma, or shock. They are used in lower doses to treat allergic reactions such as heaves, hives, itching, and inflammatory diseases including arthritis.
Dexamethasone 21 isoniconate is generally used as an
anti-inflammatory drug in the treatment of musculoskeletal problems. It
should not be used to the exclusion of other forms of therapy and it should
not be used in conditions requiring prolonged therapy. Dexamethasone 21
isoniconate is given by intra-muscular injection.
• Systemic side effects to corticosteroids are generally dependent on dose and duration of treatment. Adrenocorticosteroids have effects on every body system. All of the side effects and precautions for corticosteroid use are applicable when using dexamethasone 21 isoniconate.
• Administration of exogenous corticosteroids can suppress the body's normal production of these hormones.
• Adverse effects due to corticosteroid treatment usually occur with long-term administration of the drug, especially when high doses are used. If possible, the longer acting corticosteroids should be avoided for long-term therapy. Alternate day therapy with short acting preparations is preferred. Animals who have received long-term therapy should be withdrawn slowly by tapering the dosage and prolonging the interval between doses.
• Corticosteroids suppress immune response. Horses receiving systemic corticosteroids may be more susceptible to bacterial or viral infections. Systemic corticosteroids can mask signs of infection, such as an elevated temperature.
• 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 the dexamethasone drugs have not historically been considered to be in this 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 may already 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 in cattle. Although it is not well documented, they may present a similar risk in mares in late pregnancy.
• Corticosteroids should be avoided in young foals because of immune suppression. When used in foals, they are frequently prescribed with anti-ulcer medication because of the increased risk of GI ulcers in this population.
• When diuretics such as furosemide are given with corticosteroids, there is an increased risk of electrolyte imbalances due to calcium and potassium losses.
• 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 NSAIDs are given at the same time.
Short-term administration is unlikely to cause serious harmful systemic effects due adrenal suppression but laminitis is always an area of concern with an overdose of corticosteroids.
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 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
The information contained on this site
is general in nature and is intended for use as an informational aid. It does
not cover all possible uses, actions, precautions, side effects, or interactions
of the products shown, nor is the information intended as medical advice or
diagnosis for individual health problems or for making an evaluation as to the
risks and benefits of using a particular product. You should consult your doctor
about diagnosis and treatment of any health problems. Information and statements
have not been evaluated by the Food and Drug Administration ("FDA"),
nor has the FDA approved the products to diagnose, cure or prevent disease.
Wedgewood compounded veterinary medicines are not intended for use in food and food-producing animals.
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