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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.

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

Common Uses for prescription Corticosteroids

1. Antiinflammatory

• anti-itch (skin problems)
• anti-swell (soft tissue and skeletal trauma, spinal cord and head injury)
• anti-pain
• anti-other inflammatory reactions

2. Immune Suppression/Neoplasia

• immune-system mediated diseases (various skin disorders, muscle and joint disorders, blood and marrow disorders)
• neoplasia (part of chemotherapy protocol for specific forms of cancer)

3. Other Conditions

• vitamin D intoxicosis (certain rat baits)
• certain forms of hypercalcemia (when blood calcium is way too high)
• hypoadrenocorticism (Addison's Disease)

 

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

• increased appetite

• increased thirst (and in frequency of urination)

• suppression of the immune system: increased incidence of infections including skin, urinary tract, respiratory tract

• poor wound healing, tendon, ligament and joint abnormalities

• dull/dry hair coat or hair loss, dry, thin skin that bruises readily

• decreased muscle mass and tone...(weakened abdominal muscles may result in a "pendulous [pot-belly] abdomen"); muscle pain, stiff gait, rigid limbs (may mimic a hip or other joint disease)

• panting

• vomiting and/or bloody diarrhea, ulcers due to:

  1. a. decrease production of protective gastointestinal tract lining

  2. increased irritation from stomach acid secretion

• enlarged liver/impaired liver function

• thromboembolus (inappropriate blood clot...can suddently impair blood flow to any organ system with potentially dire consequences)

• hypertension (elevated blood pressure)

• diabetes

• pancreatitis

• osteoporosis

• changes in genital / reproductive organs

• hypothyroidism

• behavioral abnormalities including depression, aggression/ rage, mania, hyperactivity

• protracted and/or oversupplementation then abrupt cessation of prescription corticosteroids (injectable, oral and topical preparations) interferes with the usual molecular signals which turn on or off the natural physiological production of glucocorticoids by the adrenal glands...(affectionately referred to as the "HPA "....the Hypothalamic-Pituitary-Adrenal axis); these glands, in turn, may "shrink" (atrophy) due to lack of stimulation creating the possibility of inadequate blood cortisol concentrations for days, weeks or longer after cessation of treatment

• animals are unable to appropriately secrete glucocorticoid when needed.and a hypoadrenocortical "crisis" may ensue.

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

 

• excessive dose, frequency or duration of treatment with any corticosteroid

• long-acting injectable (repository) corticosteroid treament (duration of effect is not always predictable)

• frequent high or intermediate potency injectable, oral or topical corticosteroid preparations (this means that glucocorticoids in topical medication for eyes, ears or skin are also absorbed into the bloodstream and can produce any or all of the undesirable effects described above).

• When treatment with short-acting oral preparation is at high doses or prolongued (greater than two to three weeks) OR if long-acting and/or potent corticosteroids are administered the HPA is usually corrupted, though not irreversibly

• to safely allow the HPA and adrenal gland, in particular, to resume normal functional status, a gradual, step-wise decrease in frequency and dose of medication is recommended (usually over a period of days or weeks) rather than abrupt withdrawal.