Corticosteroids: best avoided in rabbits !!!
Esther van Praag, Ph.D.
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Corticosteroids are steroid hormones that are naturally present in the body of mammals. They are produced in the adrenal cortex of the adrenal glands, located above the kidneys. Two types of corticosteroids are produced in the body:
· Glucocorticosteroids like cortisol;
· Mineralocorticosteroid like aldosterone.
Nowadays, different chemical corticosteroids (also referred to as steroids) are synthesized in pharmaceutical laboratories and mimic the effects of the natural molecules. The most common ones used in veterinary medicine and given to rabbits include dexamethasone, prednisone, and methylprednisolone.
Natural and chemical corticosteroids play an important role in physiological and metabolic processes and can affect recovery.
Glucocorticosteroids lead to:
· Response to stress, e.g. handling during an examination at the vet clinic can lead to a sudden increase of cortisol in the blood in rabbits;
· Control of the carbohydrate, fat and protein metabolism;
· Depression of the mechanism of immune response against pathogen agents, e.g., natural and chemical glucocorticosteroids decrease the eosinophil reaction;
· Anti-inflammatory action, by preventing the release of phospholipids.
Mineralocorticosteroids play an important role in:
· Control of water levels, blood electrolyte levels;
· Blood pressure.
In what form are glucorticosteroids available?
Corticosteroid preparation are available for systemic (throughout the whole body) or topical (local) use. They include injection solutions, oral medicines, drops and creams.
How do chemical glucocorticosteroids act?
Chemical glucocorticosteroids act by decreasing inflammation in tissues. Inflammation is the result of an injury, an attack by a foreign pathogen, e.g., bacteria, fungi, protozoa, etc., or an allergic reaction and is characterized by swelling, redness, warmth and possibly pain. Inflammation of tissues must be reduced in order to avoid damage to tissues or organs and to reduce compression of nerves.
Unfortunately, chemical corticosteroids also depress the activity of the immune system, reducing the ability of the body to defend itself properly against infection caused by these foreign bodies. Indeed, white blood cells will be prevented from defending the body and from fighting the disease or the foreign bodies. As a result, the bacteria, fungi or protozoa survive and cause more damage. The disease becomes worse, e.g. malasseziasis occurs as a result of change from commensal to abnormal pathogen growth, in animals and rabbits whose immune system is weakened by disease, stress, or prolonged administration of antibiotics or corticosteroids (Lehmann, 1985; Hunt, 2009).
When are glucocorticosteroids used?
Glucocorticosteroids should only be given to rabbits when:
· The rabbit is in shock, e.g. after a spine fracture, but never longer than for 3 to 5 days.
· The rabbit suffers an allergic reaction (rare), or when the immune system of the rabbit is malfunctioning, attacking its own body and causing tissue damage (autoimmune disease, also rare). They are not useful in case of acute anaphylactic reaction, but may help prevent a relapse at a later time.
· Skin pruritus - to relieve the sensation of itching in the skin, when this is severe and cannot be relieved with other medication, and to avoid auto-mutilation or further damage of a limb or digit. It will not ease the rabbit's discomfort.
· Swelling of tissues inside the body when this is severe and threatens to damage critical body organs.
The use of corticosteroids should be avoided as they act as strong immunodepressants in rabbits (Jeklova et al., 2008). Furthermore, administration of steroids - in particular long-acting corticosteroids, can lead to serious side effects in rabbits:
· Gastro-intestinal ulcerations and hemorrhages;
· Hormonal imbalance due to suppression of adrenal gland activity;
· Delayed wound healing;
· Immunosuppression, permitting flare ups of latent bacterial or parasitic infections.
Safe alternatives to glucocorticosteroids
Treatment alternatives should be considered instead:
· In case of infections caused by pathogens like e.g. bacteria, fungi or yeasts, protozoa like Encephalitozoon cuniculi, inflammation of the tissue can be successfully controlled with the administration of NSAIDs analgesics (pain killers) over a longer period of time, with fewer or less severe side effects. This is especially true in the case of bacterial middle/inner infection (otitis media/interna) and during an active phase of encephalitozoonosis.
· If the skin is pruritic, anti-histamine drugs can be given. Compared to corticosteroids, their side-effects are fairly mild in rabbits, mainly sedation.
In humans topical administration of unrefined, organic sesame oil was shown to be effective in the treatment of pruritus, without the undesirable side effects of corticosteroids. It appears to successfully decrease pruritus in rabbits as well (information gathered via personal conversations).
Concurrent administration of corticosteroids and NSAID analgesics can exacerbate the negative effect on the gastro-intestinal system (Oglesbee, 2006; Pratt et al., 1999).
Many thanks for Rosalyn Lamb (Rabbit Welfare Association & Fund) for her suggestion of a page about corticosteroids
and their use in rabbits and editing help.