甲基普賴鬆 / 甲基培尼皮質醇
甲基普賴鬆是一種合成的中效**糖皮質激素**，其效力約為氫化可的松的4至5倍，且幾乎不具鹽皮質激素活性。在獸醫學中廣泛用於其強效的抗發炎和免疫抑制特性。 **臨床要點與劑型：** * **甲基普賴鬆鹼基：** 用於口服錠劑，適合維持或遞減療法。 * **醋酸甲基普賴鬆 (Depo-Medrol®)：** 微晶懸浮液，用於肌肉內、病灶內或關節內注射。吸收緩慢，提供長效儲積作用（數週至數月）。**注意：** 可能導致嚴重且長期的下視丘-腦下垂體-腎上腺 (HPA) 軸抑制。 * **琥珀酸鈉甲基普賴鬆 (Solu-Medrol®)：** 高度水溶性酯類，專為急性危急情況（如脊髓創傷、嚴重過敏反應、休克）的快速靜脈注射而設計，儘管高劑量用於休克/創傷的爭議日益增加。 雖然非常有效，但糖皮質激素治療的目標始終是**在最短時間內使用最低有效劑量**，以盡量減少全身性不良反應，特別是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 by diffusing across cell membranes and binding to specific **cytoplasmic glucocorticoid receptors (GR)**. * **Genomic Pathway:** The receptor-ligand complex translocates to the nucleus → binds to **glucocorticoid response elements (GREs)** on target genes → alters gene transcription. * **Anti-inflammatory Mechanism:** They induce the synthesis of **lipocortin-1 (annexin-1)** → inhibits **phospholipase A2** → blocks the release of arachidonic acid from membrane phospholipids → profoundly decreases the synthesis of pro-inflammatory **prostaglandins and leukotrienes**. * **Immunosuppressive Mechanism:** They suppress the transcription of inflammatory cytokines (e.g., IL-1, IL-2, IL-6, TNF-alpha), inhibit macrophage and neutrophil migration/function, and induce apoptosis in lymphocytes. * **Metabolic Effects:** Stimulate hepatic gluconeogenesis, promote protein catabolism, and redistribute lipid stores.
各物種劑量
- Labeled uses (Oral) · Cats weighing 5-15 lbs: 2 mg; Cats weighing >15 lbs: 2-4 mg; these total daily doses should be divided · PO · q6-10h · Divide total daily dose and give 6-10 hours apart.
- Labeled uses (Injectable) · up to 20 mg (average 10 mg) · IM · May repeat at weekly intervals · Depending on breed (size), severity of condition, and response.
- Intralesional (sub-lesional) use · 10-40 mg total dose · intralesional · A sufficient volume of 20 mg/mL methylprednisolone acetate is used to undermine the lesion.
- Antiinflammatory (glucocorticoid effects) · 200 mg · IM · repeated as necessary · Labeled use.
- Intra-articular use · 100 mg · IA
- Labeled uses (Oral) · Dogs weighing 5-15 lbs: 2 mg; Dogs weighing 15-40 lbs: 2-4 mg; Dogs weighing 40-80 lbs: 4-8 mg; these total daily doses should be divided · PO · q6-10h · Divide total daily dose and give 6-10 hours apart.
- Labeled uses (Injectable) · 2-120 mg (average 20 mg) · IM · May repeat at weekly intervals · Depending on breed (size), severity of condition, and response.
- Intralesional (sub-lesional) use · 10-40 mg total dose · intralesional · A sufficient volume of 20 mg/mL methylprednisolone acetate is used to undermine the lesion.
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給藥途徑
禁忌症
- Systemic fungal infections (unless used for Addison's replacement)
- Viral infections
- Arrested tuberculosis
- Peptic or corneal ulcers
- Acute psychoses
- Cushingoid syndrome
- Idiopathic thrombocytopenia (for IM administration)
- Acute local infections (for intrasynovial/intratendinous use)
- Chronic systemic therapy using sustained-release injectable forms
- Pregnant animals
- Renal disease
- Diabetes mellitus
不良反應
- Polyuria (PU), polydipsia (PD), polyphagia (PP)
- Iatrogenic hyperadrenocorticism (Cushingoid signs) with sustained use
- HPA axis suppression
- Weight gain and lipidemias
- Dull, dry haircoat and alopecia
- Muscle wasting and weakness
- Gastrointestinal ulceration, vomiting, diarrhea, melena, hematochezia
- Elevated liver enzymes (ALP, ALT) and hepatopathy
- Pancreatitis
- Activation or worsening of diabetes mellitus (especially in cats)
- Behavioral changes (depression, lethargy, viciousness, panting)
- Extracellular hyperglycemia leading to volume expansion and potential CHF (cats)
- Hypothalamic-pituitary-adrenal (HPA) axis suppression
- Adrenal atrophy
- Weight loss (catabolic effect)
藥物相互作用
- Amphotericin B · May cause hypokalemia; potential for CHF and cardiac enlargement · moderate
- Analgesics/Opiates/Local Anesthetics (epidural) · Combination in epidurals has caused serious CNS injuries and death
- Anticholinesterase agents (e.g., pyridostigmine) · May lead to profound muscle weakness in myasthenia gravis patients
- Aspirin · Glucocorticoids may reduce salicylate blood levels
- Barbiturates · May increase the metabolism of glucocorticoids and decrease blood levels
- Cyclophosphamide · Glucocorticoids may inhibit hepatic metabolism of cyclophosphamide
- Cyclosporine · May mutually inhibit hepatic metabolism, increasing blood levels of both drugs
- Potassium-depleting diuretics · May cause hypokalemia
- Ephedrine · May reduce methylprednisolone blood levels
- Estrogens · May potentiate the effects of methylprednisolone
- Insulin · Insulin requirements may increase due to glucocorticoid-induced insulin resistance · moderate
- Ketoconazole and Azole Antifungals · May decrease metabolism of glucocorticoids; ketoconazole may induce adrenal insufficiency upon withdrawal
監測
- Weight, appetite, and signs of edema
- Serum and/or urine electrolytes
- Total plasma proteins, albumin
- Blood glucose
- Growth and development in young animals
- ACTH stimulation test (if iatrogenic Cushing's or Addison's is suspected)
- Clinical signs of iatrogenic hyperadrenocorticism (PU/PD, polyphagia, weight gain)
- Blood glucose levels (especially in diabetic or pre-diabetic patients)
- Serum electrolytes (specifically potassium)
- Thyroid panel (T3 and T4 may be artificially decreased)
- Signs of gastrointestinal ulceration (melena, vomiting blood)
過量
Short-term administration of massive doses is unlikely to cause harmful effects, though one case of acute CNS effects in a dog after accidental ingestion has been reported. If acute overdose occurs, provide supportive treatment as required. **Chronic Overdosage:** Chronic usage leads to serious adverse effects, primarily iatrogenic hyperadrenocorticism (Cushing's syndrome), characterized by profound metabolic, dermatologic, and immunosuppressive changes.
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