Glucocorticoids are possibly the most commonly used single drug class in veterinary medicine. The fact that they are useful in a wide variety of conditions, cheap, versatile, relatively safe, and can have potent and dramatic effects when used properly ensures they will continue to be popular with veterinarians. It may be this popularity that has led to the statement "no animal should die without the benefit of steroids!" However, because glucocorticoids have been around for so long and are used so routinely we as veterinarians may sometimes overlook some basic, but vital, information about these drugs.
What DON'T steroids do?
Glucocorticoids affect nearly every body system and produce a wide range of effects depending on the drug concentration and specific location. You may recall some of this information from introductory physiology...
- Metabolism: glucocorticoids raise blood glucose through increasing gluconeogenesis and antagonizing insulin. They also alter protein and fat metabolism.
- Anti-inflammatory effects: inhibits arachadonic acid formation leading to ( prostaglandin, thromboxane, and leukotrienes. Can also ( neutrophil migration into tissue and increase membrane stability.
- Water balance: increase in glucose and/or sodium can osmotically increase plasma volume, often resulting in PU/PD (especially in dogs).
- CNS: steroids can improve mood, behaviour, and appetite, but may lower seizure threshold.
- GI: steroids are ulcerogenic due to increased secretion of gastric acid, pepsin, and trypsin. This effect is synergistic with NSAIDs.
- Adrenal axis suppression: exogenous glucocorticoids will suppress ACTH secretion, which can lead to adrenal gland atrophy.
- Immunosuppression: at high doses, the anti-inflammatory effects resulting from altered leukocyte movement and function can become immunosuppressive.
- Phosphate and succinate esters are water-soluble and act the most rapidly. These are the "shock" treatment steroids.
•Methylprednisolone sodium succinate (Solu-Medrol® )
•Prednisolone sodium succinate (Solu-Delta-Cortef®)
•Dexamethasone sodium phosphate (Dexaject SP®)
- Free steroid alcohol solutions are not quite as rapid acting, but can be given IV or IM and are useful for acute conditions like vaccine reactions and insect bite hypersensitivity.
•Dexamethasone (Azium(, Dexaject®)
- Acetate and acetonide esters are poorly water-soluble and given IM, SC, or intraarticular. They are absorbed slowly and will cause adrenal gland suppression.
•Methylprednisolone acetate (Depo-Medrol®)
- Oral formulations are well absorbed in dogs and cats and come in numerous brands and concentrations.
•Dexamethasone tablets and powder
Adverse effects of glucocorticoids
As we all know, steroids can cause adverse effects in small animals, especially if given at high doses or for extended periods of time. Negative effects include:
- Metabolic: diabetes mellitus, hyperlipidemia, hepatopathy
- Musculoskeletal: muscle atrophy, ligament weakness
- Immunosuppression: increased risk of infection and septicemia
- Endocrine: hypothalamo/pituitary axis suppression, thyroid and parathyroid suppression
- GI: gastric ulcers, pancreatitis
- Fluid balance: water retention, PU/PD
- Anaphylactic reactions