Glucocorticoids
Glucocorticoids are a broad class of steroid hormones with profound effects on virtually every cell type and system in mammals. In veterinary medicine, they are utilized across four broad dosage ranges and indications: * **Physiologic Replacement:** For patients with adrenal insufficiency (e.g., Addison's disease). * **Anti-inflammatory:** To manage allergic states, respiratory diseases (asthma), dermatologic conditions, and osteoarthritis. * **Immunosuppressive:** For autoimmune disorders such as immune-mediated hemolytic anemia (IMHA), thrombocytopenia, pemphigus, and systemic lupus. * **Antineoplastic:** Used as cytotoxic agents in certain neoplasias (e.g., lymphoma). **Clinical Pearl:** Cats generally require higher dosages than dogs to achieve the same clinical effect but tend to be more resistant to developing adverse effects. Conversely, dogs are highly sensitive to glucocorticoids and readily develop iatrogenic hyperadrenocorticism (Cushing's syndrome) with chronic use.
กลไกการออกฤทธิ์: Glucocorticoids exert their effects primarily by binding to cytosolic **glucocorticoid receptors (GR)**. The receptor-ligand complex translocates to the nucleus, where it binds to glucocorticoid response elements (GREs) on DNA, altering gene transcription (transactivation and transrepression). * **Anti-inflammatory Pathway:** They induce the production of **lipocortin (annexin-1)**, which inhibits **phospholipase A2**. This blocks the release of **arachidonic acid** from cell membranes → dramatically decreasing the synthesis of both **prostaglandins** and **leukotrienes**. * **Immune Suppression:** They inhibit macrophage function, decrease circulating T-lymphocytes, suppress inflammatory cytokines (IL-1, IL-6, TNF-alpha), and inhibit the complement cascade. * **Metabolic Effects:** Stimulate gluconeogenesis, mobilize amino acids, and redistribute adipose tissue, which can lead to insulin resistance.
ขนาดยาตามชนิดสัตว์
- Anti-inflammatory (Prednisolone equivalent) · 1.0-2.0 mg/kg · PO · q12h to q24h · Taper to lowest effective alternate-day dose · Cats require higher doses than dogs and should receive prednisolone, not prednisone.
- Immunosuppressive (Prednisolone equivalent) · 2.0-4.0 mg/kg · PO · q12h to q24h · Taper slowly over weeks to months · Monitor for signs of diabetes mellitus.
- Anti-inflammatory (Prednisolone equivalent) · 0.5-1.0 mg/kg · PO · q12h to q24h · Taper to lowest effective alternate-day dose · Doses are highly variable depending on the specific glucocorticoid used.
- Immunosuppressive (Prednisolone equivalent) · 2.0-4.0 mg/kg · PO · q24h (divided q12h initially) · Taper slowly over weeks to months · Monitor closely for severe adverse effects at these doses.
ขนาดยาเป็นข้อมูลอ้างอิงทางคลินิกสำหรับสัตวแพทย์ผู้มีใบอนุญาต โปรดตรวจสอบกับฉลากล่าสุดและผู้ป่วยแต่ละรายเสมอ
วิธีการให้ยา
ข้อห้ามใช้
- Systemic fungal infections (unless used for physiologic replacement)
- Intramuscular administration in patients with idiopathic thrombocytopenia
- Known hypersensitivity to the specific compound
- Chronic use of sustained-release injectables for systemic diseases
- Concurrent use with NSAIDs (relative contraindication due to severe GI ulcer risk)
- Pregnant animals
- Renal disease (systemic use)
- Diabetes mellitus (systemic use)
- Systemic fungal infections
- Corneal ulcers
- Concurrent use of NSAIDs
- Uncontrolled diabetes mellitus
- Late pregnancy (may induce abortion or parturition)
อาการไม่พึงประสงค์
- Polyuria (PU), polydipsia (PD), and polyphagia (PP)
- Weight gain and fat redistribution
- Panting (especially in dogs)
- Dull, dry haircoat and alopecia
- Vomiting and diarrhea
- Gastrointestinal ulceration
- Elevated liver enzymes (ALP > ALT) and vacuolar hepatopathy (dogs)
- Pancreatitis
- Insulin resistance leading to or worsening diabetes mellitus
- Muscle wasting and weakness
- Behavioral changes (depression, lethargy, viciousness)
- Iatrogenic hyperadrenocorticism (Cushing's syndrome) with chronic use
- Laminitis (horses)
- Hypothalamic-pituitary axis (HPA) suppression
- Adrenal atrophy
อันตรกิริยาระหว่างยา
- Amphotericin B · May cause hypokalemia when administered concomitantly
- Anticholinesterase agents (e.g., pyridostigmine) · May lead to profound muscle weakness in myasthenia gravis patients; discontinue 24h prior if possible
- Aspirin (salicylates) · Glucocorticoids may reduce salicylate blood levels; increased risk of GI ulceration
- Cyclophosphamide · Glucocorticoids may inhibit hepatic metabolism of cyclophosphamide
- Cyclosporine · May mutually inhibit hepatic metabolism, increasing blood levels of both drugs
- Digoxin · Increased risk for arrhythmias secondary to glucocorticoid-induced hypokalemia
- Diuretics (potassium-depleting, e.g., furosemide) · May cause additive hypokalemia
- Ephedrine · May increase glucocorticoid metabolism
- Estrogens · May potentiate the effects of hydrocortisone and possibly other glucocorticoids
- Insulin · Insulin requirements may increase due to glucocorticoid-induced insulin resistance · moderate
- Ketoconazole · May decrease glucocorticoid metabolism
- Mitotane · May alter steroid metabolism; higher steroid doses may be necessary to treat mitotane-induced adrenal insufficiency
การติดตาม
- Weight, appetite, and signs of edema
- Serum and/or urine electrolytes (potassium, calcium, sodium)
- Total plasma proteins and albumin
- Blood glucose
- Liver enzymes (ALP, ALT, GGT)
- Growth and development in young animals
- ACTH stimulation test (if assessing adrenal recovery or iatrogenic Cushing's)
- Clinical signs of hyperadrenocorticism
- Blood glucose (especially in diabetics)
- Electrolytes (potassium)
- Thyroid panel (T3/T4 may decrease)
- Clinical signs of PU/PD and weight gain
- Blood glucose (due to diabetes mellitus risk)
- ACTH stimulation test (to monitor HPA axis suppression)
- Water intake and urine output
การได้รับยาเกินขนาด
Short-term massive overdoses are unlikely to cause acute harmful effects, though one case of acute CNS effects in a dog has been reported (treat supportively). Chronic overdosage leads to serious adverse effects manifesting as iatrogenic hyperadrenocorticism (Cushing's syndrome).
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