氟氫可的松
氟氫可的松是一種強效的口服**合成皮質類固醇**，主要用於獸醫學中的**鹽皮質激素**特性。 * **主要適應症：** 它是犬貓**腎上腺皮質機能減退症（愛迪生氏病）**的主要治療藥物，作為注射型 DOCP 的口服替代方案。 * **雙重作用：** 雖然主要利用其鹽皮質激素效應（效力為氫化可的松的 125 倍），但它也具有顯著的**糖皮質激素活性**（效力為氫化可的松的 10-15 倍）。 * **臨床要點：** 由於其固有的糖皮質激素活性，約 50% 使用氟氫可的松控制的犬隻不需要額外每日補充潑尼松/潑尼松龍（與使用 DOCP 的病患不同）。然而，在較高劑量下，這種糖皮質激素活性也可能導致醫源性腎上腺皮質機能亢進的症狀（多渴/多尿、多食）。
作用機制: Fludrocortisone acts as a potent agonist at mineralocorticoid receptors. * Binds to **cytosolic mineralocorticoid receptors** in the principal cells of the **renal distal tubules** and **collecting ducts** → translocates to the nucleus. * Upregulates the transcription of **epithelial sodium channels (ENaC)** on the apical membrane and **Na+/K+-ATPase pumps** on the basolateral membrane. * This mechanism → promotes active **sodium reabsorption** (and obligate water retention) while accelerating the excretion of **potassium** and **hydrogen ions** into the tubular lumen. * Also binds to **glucocorticoid receptors**, contributing to anti-inflammatory and metabolic effects (gluconeogenesis, protein catabolism).
各物種劑量
- Maintenance therapy of hypoadrenocorticism · 0.02 mg/kg PO once daily · PO · once daily · Prednisone or prednisolone (1.25 mg per cat PO once daily) can be used for glucocorticoid replacement.
- Maintenance therapy of hypoadrenocorticism · 0.1 mg total dose/cat PO once daily · PO · once daily · Administer with prednisolone (0.2 mg/kg PO once daily).
- Hypoadrenocorticism · 0.05-0.1 mg/kg PO q24h or divided q12h · PO · q24h or divided q12h · For those animals that still exhibit Addisonian signs even with prednisone therapy.
- Hypoadrenocorticism · Initial dose of 0.01 mg/kg PO twice daily · PO · twice daily · Adjust dose based on monitoring serum electrolyte concentrations every 1-2 weeks until stable. Once stable, recheck every 3-4 months. Addition of NaCl (0.1 g/kg/day) can be useful in reducing the dose of fludrocortisone and reducing PU/PD.
- Maintenance of hypoadrenocorticism · Initially, 0.01-0.02 mg/kg/day PO and adjusted by 0.05-0.1 mg (total dose) increments · PO · daily · Adjust based on serial electrolyte determinations. Most dogs will ultimately require 0.02-0.03 mg/kg/day.
- Hypoadrenocorticism · 0.01 mg/kg PO twice daily · PO · twice daily · Titrate dose to effect; typically dose needs to be increased over time. Only 50% of dogs on fludrocortisone require supplemental prednisone.
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
- Known hypersensitivity to fludrocortisone
不良反應
- Polyuria (PU)
- Polydipsia (PD)
- Hypertension
- Edema
- Hypokalemia
- Hypernatremia
- Signs of iatrogenic Cushing's syndrome (due to glucocorticoid effects)
藥物相互作用
- Amphotericin B · Patients may develop hypokalemia if administered concomitantly.
- Aspirin · Fludrocortisone may reduce salicylate levels.
- Potassium-depleting diuretics (e.g., thiazides, furosemide) · May cause hypokalemia; diuretics can cause sodium loss, counteracting the effects of fludrocortisone.
- Insulin · Potentially increases the insulin requirements of diabetic patients.
監測
- Serum electrolytes (Sodium, Potassium)
- BUN and Creatinine
- Body weight
- Physical examination for signs of edema or hypertension
- Clinical signs of PU/PD
過量
Overdosage is typically characterized by excessive mineralocorticoid effects: * **Clinical Signs:** Hypertension, edema, severe hypokalemia, and hypernatremia. Excessive glucocorticoid signs (severe PU/PD, panting) may also occur. * **Management:** Discontinue the drug until clinical signs associated with overdosage have resolved. Electrolytes should be aggressively monitored. Potassium supplementation may be required. Once resolved, restart the drug at a lower dosage.
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