By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Brand Name: Azium, Voren
Available in 0.25 mg, 0.50 mg, 0.75 mg, 1 mg, 1.5 mg, 2 mg, 4 mg and 6 mg tablets; oral solution; several eye drop formulations
Uses of this Medication
Dexamethasone is a member of the glucocorticoid class of hormones. This means they are steroids but, unlike the anabolic steroids that we hear about regarding sports medicine, these are catabolic steroids. Instead of building the body up, they are designed to break down stored resources (fats, sugars and proteins) so that they may be used as fuels in times of stress. Cortisone would be an example of a related hormone with which most people are familiar, though cortisone (more correctly called cortisol) is a natural hormone produced by the body's adrenal glands, whereas dexamethasone is synthetic.
In most cases, we do not use glucocorticoids for their influences on glucose and protein metabolism; we use them because in higher doses they are broadly anti-inflammatory. Their uses fit into several groups:
- Anti-inflammatory - especially for joint pain and itchy skin.
- Immune-suppression - treatment of conditions where the immune system is destructively hyperactive. Higher doses are required to actually suppress the immune system.
- Cancer chemotherapy - although usually prednisolone, another steroid, is favored for this use.
- Central nervous system disorders - usually after a disk episode to relieve swelling in the spinal cord.
- Blood calcium reduction - in medical conditions where blood calcium is dangerously high and treatment is needed to reduce levels to normal.
- Dexamethasone also has some use in pregnancy termination in dogs.
Dexamethasone is commonly used for several weeks or even months at a time to get a chronic process under control. Once the condition is controlled, it is important that the dose be tapered to the lowest effective dosing frequency once the condition is controlled. The reason for this is that body will perceive these hormones and not produce any of its own. In time, the adrenal glands will atrophy so that when the medication is discontinued, the patient will be unable to respond to any stressful situation. A blood sugar crisis can result. By using the medication every other day, this allows the body's own adrenal glands to remain active.
Any latent infections can be unmasked by dexamethasone use. (Feline upper respiratory infections are a classical example. When a cat recovers clinically, the infection simply goes dormant. Glucocorticoid use could bring the infection out again.)
Glucocorticoid hormone use can be irritating or even ulcerating to the stomach or intestine at higher doses.
Long-term steroid use strongly predisposes a patient to latent urinary tract infection. Such infections may not have apparent symptoms because the inflammation responsible for the symptoms is suppressed by the steroid.
Glucocorticoids are called diabetogenic hormones, which means that with long-term use or in predisposed patients they can induce diabetes mellitus. They should not be used in patients who already have diabetes mellitus.
Interactions with other Drugs
Glucocorticoid hormones should not be used in combination with medications of the NSAID class (i.e. aspirin, carprofen, meloxicam, etc.) as the combination of these medications could lead to bleeding in the stomach or intestine. Ulceration could occur.
Macrolide antibiotics (such as clarithromycin or erythromycin) can increase dexamethasone blood levels. Use of the antifungal ketoconazole can have a similar interaction.
Diuretics that work by reducing blood potassium levels can create significantly low blood potassium levels when combined with dexamethasone.
Concerns and Cautions
Dexamethasone is considered to be a long-acting steroid, meaning that a dose lasts about two or two-and-a-half days. For this reason an every other day schedule is excessive for dexamethasone; every third day or less is the goal for dexamethasone.
The same salt retention that accounts for excessive thirst and urination may also be a problem for heart failure patients or other patients who require sodium restriction.
Diabetic patients should never take this medication unless there is a life-threatening reason why they must.
Glucocorticoid hormones can cause abortion in pregnant patients. This class of hormone should not be used in pregnancy.
Dexamethasone use is likely to change liver enzyme blood testing and interfere with testing for thyroid diseases.
Dexamethasone is approximately 10 times stronger than prednisone/prednisolone.
Monitoring tests will likely be recommended if this medication is used long term.
Read more about chronic steroid use.
Read more about steroid alternatives for relieving itchy skin.
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