Dexamethasone

Dexamethasone: Uses, Dosage and Side Effects

Overview

• Modifies the transcription of DNA, resulting in changes in cellular metabolism that reduce the inflammatory response.

Uses of Dexamethasone

• Anti-inflammatory drug.
• Assessment of adrenal function in suspected hyperadrenocorticism (HAC).
• Dexamethasone suppression tests.
• Emergency treatment of hypoadrenocorticism.
• To prevent and treat anaphylaxis associated with a transfusion or chemotherapeutic agents.

Dose of Dexamethasone in Dogs and Cats

Dogs:

• Ophthalmic: Apply a small amount of ointment to the affected eye(s) q6–24h or 1 drop of solution in the affected eye(s) q6–12h.
• Otic: 10 drops to ear once daily for 7–14 days
• Cerebral edema associated with tumors: anti-inflammatory dose 0.1–0.3 mg/kg.
• Hypoadrenocorticism: 0.2 mg/kg i.v. repeat daily until able to use oral medication.
• Inflammation: 0.01–0.16 mg/kg i.m., s.c., p.o. q24h for 3–5 days maximum.
• Prevention and treatment of anaphylaxis: 0.5 mg/kg i.v. once.
• Immunosuppression: 0.3–5 mg/kg i.m., s.c., p.o. q24h for up to 5 days.
• Assessment of adrenal function: low dose dexamethasone suppression test (0.01–0.015 mg/kg i.v.).

Cats:

• Ophthalmic, cerebral edema, inflammation, anaphylaxis, immunosuppression: doses as for dogs.
• Assessment of adrenal function: dexamethasone suppression test (0.1–0.15 mg/kg i.v.). Note the difference to dogs.

Side Effects of Dexamethasone in Dogs and Cats

• One dose of dexamethasone or sodium phosphate suppresses adrenal gland activity for 32 hours.
• Long-term glucocorticoid use inhibits the hypothalamic–pituitary axis (HPA)  causing adrenal atrophy.
• Increased liver enzyme activity, cutaneous atrophy, weight loss, PU/PD, vomiting, and diarrhea.
• Possible GI irritation.
• Dexamethasone may cause hyperglycemia and low blood T4.

Contraindications of Dexamethasone in Dogs and Cats

• Pregnancy.
• Renal illness and diabetes.
• Infections and wound healing may be slowed.
• Ulcerative keratitis contraindicates topical corticosteroids.

Some Notes:

• Prednisolone is 7.5 times weaker. 0.15 mg dexamethasone equals 1 mg prednisolone.
• Dexamethasone is ideal for short-term high-dose therapy in cases of water retention due to its long period of action and low mineralocorticoid activity.
• Long-term daily or alternate-day use is unsuitable.
• Discontinuing steroids in chronically treated animals requires tapering.
• Long-acting steroids in shock and spinal damage are usually harmful.
• NSAIDs raise GI ulcer risk.
• Corticosteroids and amphotericin B or potassium-depleting diuretics (furosemide, thiazides) raise the risk of hypokalemia.
• Dexamethasone opposes insulin.
• Phenytoin and phenobarbital increase corticosteroid absorption, while itraconazole decreases it.