.

Introduction:

Corticosteroids, when used judiciously, are an important therapeutic modality....perhaps a godsend...in veterinary medicine. However, overuse or misuse particularly in dogs*, can result in long-term undesirable effects, not the least of which is a shortening of lifespan. To minimize risk and maximize benefits, it is extremely important that when treating your pet with these drugs, you follow your veterinarian's directions regarding dose, frequency ( which may vary over days, weeks, months) and duration (length of treatment) EXACTLY as prescribed. The following is a brief, somewhat simpleminded overview of this subject, with particular emphasis on those factors bearing directly on the efficacy and safety factors which you, as a responsible pet owner, are entitled to appreciate.

 

What Are Corticosteroids?:

There are various classes of similar hormone molecules, collectively called "steroids" that are naturally synthesized by the adrenal gland from cholesterol. These are glucocorticoids mineralocorticoids, anabolic steroids, and sex hormones. This discussion will be limited to the class of molecules known as glucocorticoids.

Some Comments About Natural Regulation of Glucocorticoids

The most common naturally occuring glucocorticoids in dogs and cats are cortisone and cortisol. These ( or their synthetic equivalents) are required to sustain life! The timely release of these from the adrenal gland is, necessarily, regulated via an exquisite coordination involving 1. the "brain-hormone-feedback" ( the "HPA Feedback-Inhibition" control) mechanism and by 2. a diurnal (day/night-dependent) central nervous system controlled release mechanism. Detailed description of the former is described elsewhere on the web site. It is particularly important to realize that inappropriate use of prescription corticosteroids can adversely affect these natural controls of blood cortisol/cortisone concentrations, resulting in signs of glucocorticoid excess or deficiency, each with potentially life-threatening consequences.

Function of Glucocorticoids

Glucocorticoids affect EVERY organ body system, each in unique, simple and in quite complicated ways. It is beyond the scope of this publication to describe these in any detail. Some rather overly simplified examples are provided:

  1. Cardiovascular System: stabilize blood vessel integrity; increase cardiac muscle strength and response to neurotransmitters affecting heart rate, rhythm and force of heart muscle contraction.
  2. Kidney: affects water reabsorption and some electrolytes concentrations (more important function of mineralocorticoids).
  3. Nervous System: are necessary cofactors with epinephrine ("adrenalin"....) and similar neurotransmitters for binding of neurotransmitter to the target tissue. Without corticosteroids, the body is unable to cope with stress...a precarious and potentially life-threatening situation.
  • Stress: includes coping with changes in ambient temperature (heat and cold), restraint, pain, fear, anxiety, fear, illness, poor nutrition
  • Stress Response: includes rapid and sustained changes in: cardiovascular output (as described above), available energy resources, metabolic activity
    • increase blood supply (with oxygen and nutrients) to essential tissues (muscle, heart, brain) and decreased "wasting" of resources on non-essentials organs and (kidney, pancreas) and functions (e.g. eating, digesting, eliminating...)
    • rapid increase of energy supply...blood sugar, and fat resources, primarily via rapid response from the liver and muscle with concommitant adjustment in metabolic priorities in essential tissues and organs.

4. Digestive System: increases gastric acid, stimulates the liver as described above, involved in maintaining normal intestinal motility

5. Many, Many others functions and metabolic effects..........

Therapeutic Indications and Adverse Effects

Common Uses for prescription Corticosteroids

1. Antiinflammatory

2. Immune Suppression/Neoplasia

3. Other Conditions

 

Potential Adverse Effects of Inappropriate (potency, dose, route of administration, frequency and/or duration) Corticosteroid Therapy

  1. "Iatrogenic" Hyperadrenocorticism....similar to Cushing's Disease

2. Signs of hypoadrenocorticism (insufficient natural production of glucocorticoids from adrenal glands)

  1. anorexia, vomiting, abdominal pain,bloodly diarrhea, weight loss

  2. lethargy,

  3. dehydration, electrolyte imbalances, heart and skeletal muscle "tremors"

  4. seizures

  5. inability to adapt to stressful situations with a variety of possible outcomes, including acute collapse and death

 

3. The above adverse affects are most likely with:

4. The potential detrimental effects on the HPA seen following withdrawal of therapy is least with the short acting oral medication (especially when used for less than two weeks) and greatest with the long-acting repository injectables....or chronic, long-term use of any corticosteroid preparation.

5. *In general cats are considerably more resistant to the adverse effects of glucocorticoid thereapy than dogs, (though some speculate there is a relationship of corticosteroid "overuse" and systemic hypertension in some cats...). Therefore, the bulk of this discussion and admonitions apply primarily to canine patients.

 

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