Glucocorticoids are used commonly in many different areas of veterinary medicine. They are necessary drugs in many situations, but should always be used advisedly and with the right dosage. However, you should always be aware of their effects, their side effects to the animal body and their strong influence on laboratory examinations, which we will cover in this edition of the LABOKLIN Aktuell.
In the table 1 below are listed different duration times of various Glucocorticoids. Short acting means <12h, intermediate acting means 12- 36h and long acting means >36h. The long term effect of cortisone depends on combination of the base and the ester of the steroid, like the long acting glucocorticoids Paramethasone, Be- tamethasone and Dexamethasone, which dura- tion time lies clearly over 36 hours.
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The modality of administering cortisone also has an influence on its efficacy and duration of action. In general there is the possibility to apply Glucocorticoids orally, intramuscularly, subcu- taneously, intralesionally (e.g. in oncology), topi- cally or intravenously.
The good reasons for using Glucocorticoids (e.g. as anti-inflammatory, anti-pruritic or immuno- suppressive drug) cannot be separated from the many metabolic side effects.
Euphoria and dysphoria, behaviour and mood modifications, polyphagia and polydipsia
and seizure threshold can be lowered.
Decreased absorption of calcium and iron salts, increased fat absorption, increased secretion of gastric acid, pepsin and trypsin, vomitus, diar- rhoea, gastrointestinal ulcerations and pancreatitis.
Increased glycogen deposits within hepatocytes, increased serum levels of liver enzymes like ALT and AST and also g-GT (Gamma Glutamyl Tran- speptidase) can be increased. Severe increase of AP (alkaline Phosphatase) is frequently obser- ved: In dogs the thermally stable AP-isoenzyme is induced by endogenous or therapeutically administered Glucocorticoids, but also by many other drugs. The increase can persist up to 2-4 weeks after termination of therapy. For clarifica- tion purpose the percentage of thermally stable AP can be determined at your lab. Increased va- lues can be seen in 83-100% of dogs suffering from hyperadrenocorticism.
Muscular weakness, atrophy, osteoporosis and weight increase (adrenocortical obesity).
Skin atrophy und thinning of dermal tissue, cal- cinosis cutis, alopecia, formation of comedones, oedema and wound healing disorders
Involution of lymphatic tissue (species depen- dent), decreased amounts of lymphocytes (pe- ripheral), monocytes and eosinophils, increased amounts of peripheral neutrophils, erythrocytes and circulating platelets (platelet aggregation is inhibited though), reduced blood coagulation time, inhibited phagocytosis, reduced prostag- landin, bradykinin, histamine and interleukin pro- duction.
Positive inotropic effect, reduced capillary per- meability, enhanced vasoconstriction, arterial hypertension (retention of sodium chloride and water) and increased blood pressure (result from vaso-constrictive properties and increased blood volume).
Respiratory system: Tachypnoe (panting).
Renal, fluid and electrolytes:
Increased reabsorption of water, sodium and chloride, increased excretion of potassium and calcium and therefore increased extracellular fluid volume. Also the effect of ADH is inhibited, thus resulting in polyuria.
Inhibition of collagen synthesis carried out by fibroblasts, increased resorption of bone, decre- ased serum calcium level, vitamin D antagonist.
Suppression of the hypothalamus-pituitary gland-adrenal cortex axis, secondary hyperad- renocortisismus, secondary induced diabetes mellitus or a significant worsening of an already existing Diabetes mellitus.
Stabilization of liposomal and lysosomal mem- branes, decreased macrophage reaction to migration inhibiting factor response, decreased lymphocyte and cellular response sensitivity to mediators of inflammation and inhibition of fibro- blast proliferation.
Teratogen in early pregnancy and when adminis- tered in the latter stages of pregnancy may in- duce parturition in equine and ruminant animals (less so in dogs and cats).
Prolonged use can cause increased intraocular pressure and glaucoma, cataracts and exoph- thalmos.
Growth inhibitor in young animals (CAVE: use of glucocorticoids in young and growing animals can retard their growth).
Decreased circulating levels of T-lymphocytes, inhibition of lymphokines, inhibition of neutro- phils, macrophages and monocytes migration, reduced interferon production and inhibition of phagocytosis and chemotaxis. Glucocorticoids can also antagonize the complement cascade and mask clinical signs of infection with decrea- sed number of mast cells, suppressed histamine synthesis and reduced amount of type 1 allergic effector cells in serum (basophils). Bottom line: immunosuppression and susceptibility to infection (e.g. infections of the urinary tract).
Glucocorticoids are pronounced antiinfl drugs, which can cause suppression of symptoms of acute, chronic, immunological or non-immunological infections. Very essential is the membrane stabilizing effect, which is extended to almost all biological membranes. Thereby inhibiting degranulation and releasing of infl mediators, causing a reduction in the capillary permeability and exsudative processes. Another mechanism affects the rapidly occurring inhibiti- on of cyclooxygenase and thereby the synthesis of prostaglandins. Secondary, after a few hours, an additional blockade of the arachidonic acid cascade takes place. This early intervention in the arachidonic acid cascade not only results in the inhibition of the formation of prostaglandins but also of leucotriens. These play an important role in obstructive allergic respiratory diseases because of their vasoconstrictive effect on the bronchia.
Glucocorticoids and Allergy Testing
In cats suffering from allergic asthma a two-week withdrawal time from inhaled glucocorticoids is recommended prior to performing an intradermal skin test (IDST) (CHANG et al., 2011).
REEDY (1997) recommends a minimum of 6-8 weeks of withdrawal time after administration of injectable glucocorticoids. CLARKE et al. (2000) also found that dogs treated long term with corticoids and subsequently showed nega- tive results on the ALLERCEPT® Fce-receptor test, got positive test results after discontinu- ing of glucocorticoid therapy. Regarding orally given glucocorticoids and their influence on allergy testing KUNKLE (1994) showed that treat- ment of dogs with prednisone 1 mg/kg SID for 4-6 weeks made a significant reduction of reac- tions on the intradermal skin test (IDST). Another study showed that prednisolone and also ceti- rizine significantly influence and lower reactions in the IDST (TEMIZEL, 2011). Oral cortisone also reduces serum IgE levels considerably (SCHIESSL et al., 1998). Withdrawal times are also recommended for topical glucocorticoids and otic solutions containing cortisone. In a study 1% hydrocortisone containing conditioner (ResiCORT® Virbac) was applied once daily for 3 days. After treatment reduced IDST reactions were seen (RIVIERREL, 2000). Another study (BIZIKOVA, 2010) examined the influence of a locally used hydrocortisone aceponate spray (Cortavance® Virbac) on allergy testing. This spray reduced the IDST reactions and caused skin atrophy after long term treatment on all tre- ated areas. Therefore, it is recommended to dis- continue the applications for minimum 2 weeks prior to allergy testing.
Treatment with Otomax® (betamethasone con- taining otic solution) twice daily for 2 weeks reduced IDST reactions significantly in a study with 8 dogs (GINEL, 2007).
Although several withdrawal times regarding glu- cocorticoids, antihistamines and cyclosporine are discussed in different studies, our LABOKLIN Allergy Team recommends – based on our long clinical and laboratory experience – generally im- plementing the following withdrawal times prior to allergy testing:
Allergy is diagnosed according to clinical signs and accurate medical history, and the causative allergens are determined by allergy testing in or- der to either avoid them systematically or to per- form an allergenspecific immunotherapy (ASIT). Thus, withdrawal times should be maintained to obtain the best possible test results and blood should be collected before any therapy with glu- cocorticoids is initiated, whenever possible.
Good quality serum can be stored in the refrige- rator for a couple of weeks but frozen it can be stored for some months.
An allergy test which is performed during the glu- cocorticoid withdrawal time can be taken as valid, if it shows positive test results (reaction classes might have to be interpreted higher). In the case of negative test results, it is not possible to judge whether the result is truly negative or false negative because of the influence of gluco- corticoids on allergy testing, and re-testing after withdrawal time is recommended.