Dexamethasone for Veterinary Use

Therapeutic Class: Adrenocorticosteroid hormone

Species: Dogs, cats and horses

May Be Prescribed For: Anti-inflammatory

FDA Status: Dexamethasone is commercially available as oral concentrate1mg/ml, oral elixir/solution 0.5mg/ml, oral tablet 0.25mg, 0.5mg, 0.75mg, 1mg, 1.5mg, 2mg, 4mg, 6mg, injection solution 2mg/ml, 4mg/ml, and 10mg/ml.

Dexamethasone is a synthetic corticosteroid with approximately 25 times the anti-inflammatory potency of naturally occurring cortisol. Corticosteroids such as dexamethasone are important in normal protein, carbohydrate and fat metabolism, and for their role in controlling inflammation. These drugs have both strong beneficial effects and a definite potential to cause negative side-effects. Dexamethasone commonly is used in both small- and large-animal veterinary medicine. It may be given by injection, inhalation, orally, or topically. Preparations for topical use may include other active ingredients such as antibiotics, antifungals, or miticides.

Dexamethasone is used systemically in high doses in emergency situations for anaphylactic reactions, spinal cord trauma, or shock. It is used in manage and treat immune-mediated disease such as immune-mediated hemolytic anemia or thrombocytopenia; some cancers; allergic reactions such as asthma, hives, and itching; inflammatory diseases and some neurologic diseases. Dexamethasone also is used topically to treat a variety of skin and eye problems.

Dexamethasone is given systemically to decrease inflammatory and immune responses. It is used in high doses in emergencies for anaphylactic reactions, spinal cord trauma, or shock. It is used in lower doses to treat allergic reactions such as Chronic Obstructive Pulmonary Disease (COPD), hives, itching, inflammatory diseases including arthritis, and to manage and treat immune-mediated hemolytic anemia, and thrombocytopenia. It sometimes is used systemically as a "performance-enhancing” drug because corticosteroids decrease inflammation, possibly enhance glucose metabolism (there is some debate about this) and may have some mood elevating properties. Other corticosteroids are preferred for intra-articular use.

Systemic side-effects to corticosteroids generally are dependent on dose and duration of treatment. Adrenocorticosteroids have effects on every body system.

• Chronic or inappropriate use of corticosteroids including dexamethasone 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.

• Polyuria, polydipsia, and muscle wasting can be seen with prolonged corticosteroid use.

• Corticosteroids can cause or worsen gastric ulcers.

• 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 the dexamethasone drugs historically have 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 in cattle and has been used to terminate pregnancy in bitches.

• 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 nonsteroidal anti-inflammatory drugs are given at the same time.

• Corticosteroids should not be given intravenously with fluids containing calcium.

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 dexamethasone relate to suppression of normal adrenal function, iatrogenic Cushing's Disease and metabolic crisis due to abrupt withdrawal.