糖皮質激素
糖皮質激素是一大類對哺乳動物幾乎所有細胞類型和系統都有深遠影響的類固醇激素。在獸醫學中，它們主要用於四個廣泛的劑量範圍和適應症： * **生理性替代療法：** 用於腎上腺功能不全（如愛迪生氏症）的病患。 * **抗發炎：** 用於控制過敏狀態、呼吸道疾病（氣喘）、皮膚病和骨關節炎。 * **免疫抑制：** 用於自體免疫疾病，如免疫介導性溶血性貧血 (IMHA)、血小板低下症、天皰瘡和全身性紅斑狼瘡。 * **抗腫瘤：** 在某些腫瘤（如淋巴瘤）中作為細胞毒性藥物使用。 **臨床要點：** 貓通常需要比狗更高的劑量才能達到相同的臨床效果，但對產生副作用的抵抗力較強。相反，狗對糖皮質激素高度敏感，長期使用極易引發醫源性腎上腺皮質機能亢進（庫興氏症候群）。
作用機制: 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.
各物種劑量
- 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.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- 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)
不良反應
- 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
藥物相互作用
- 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
監測
- 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
過量
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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