異維A酸 / 異維甲酸
**異維A酸 (Isotretinoin)** 是一種第一代合成視黃醇類藥物（維A酸類），主要用於獸醫皮膚科，治療與角質化異常及皮脂腺功能障礙相關的嚴重疾病。 **主要臨床應用：** * **犬板層狀魚鱗癬 (Canine lamellar ichthyosis)** * **皮膚T細胞淋巴瘤 (Cutaneous T-cell lymphoma)** * **皮內角化上皮瘤 (Intracutaneous cornifying epitheliomas)** * **多發性表皮包涵囊腫 (Multiple epidermal inclusion cysts)** * **雪納瑞粉刺症候群 (Comedo syndrome in Schnauzers)** * **皮脂腺炎 (Sebaceous adenitis)**（特別是標準貴賓犬和維茲拉犬） * **貓粉刺 (Feline acne)** > **臨床要點：** 由於其對皮脂腺的顯著作用，異維A酸通常被認為是治療皮脂腺炎和雪納瑞粉刺症候群的首選視黃醇類藥物，而其他視黃醇類（如阿維A）可能更適合原發性角質化缺陷。 由於對人類具有嚴重的致畸胎風險（FDA懷孕用藥分級X級），製造商和經銷商可能會嚴格限制獸醫取得此藥物。
作用機制: Isotretinoin acts by regulating epithelial cell proliferation and differentiation. * **Receptor Binding:** Retinoids enter the cell and bind to intracellular **Retinoic Acid Receptors (RARs)** and **Retinoid X Receptors (RXRs)** → altering gene transcription. * **Sebosuppressive Effect:** It significantly reduces sebaceous gland size and activity → decreasing sebum production. * **Anti-keratinization & Anti-inflammatory:** Normalizes follicular desquamation (preventing comedone formation) and affects monocyte/lymphocyte function, altering cellular immune responses. * **Antimicrobial (Indirect):** By altering the microenvironment of the sebaceous pore (reducing sebum), it indirectly reduces bacterial populations.
各物種劑量
- Feline acne · 5 mg/kg PO once daily · PO · q24h
- Feline acne · 10 mg per cat once daily PO · PO · q24h
- Feline acne · 1-3 mg/kg q12-24h PO · PO · q12-24h
- Epitheliotrophic lymphoma, cutaneus lymphoma · 10 mg/cat once daily PO · PO · q24h
- Sebaceous adenitis when more conservative treatments have failed · 1 mg/kg PO q12h for one month; if improvement is noted reduce dose to 1 mg/kg PO once daily; long-term goal is to treat with either 1 mg/kg PO every other day or 0.5 mg/kg once daily · PO · q12h initially, then q24h or q48h · Long-term
- Sebaceous adenitis · 1-3 mg/kg PO once a day to twice daily · PO · q12-24h
- Schnauzer comedo syndrome · 1 mg/kg once daily or divided q12h PO · PO · q12-24h
- Sebaceous adenitis in poodles; granulomatous sebaceous adenitis in viszlas · 1-2 mg/kg once daily or divided q12h PO · PO · q12-24h
- Epitheliotrophic lymphoma, cutaneus lymphoma · 2 mg/kg once daily or divided q12h PO · PO · q12-24h
- Schnauzer comedo syndrome, sebaceous adenitis in poodles, ichthyosis, keratocanthoma, epitheliotropic lymphoma, and sebaceous gland hyperplasia and adenoma · 1-3 mg/kg q12-24h PO · PO · q12-24h
給藥途徑
禁忌症
- Pregnancy (absolute contraindication - known teratogen)
- Nursing mothers
- Hypertriglyceridemia
- Severe renal disease
- Severe hepatic disease
- Known hypersensitivity to isotretinoin
不良反應
- Dogs: Keratoconjunctivitis sicca (KCS) - most common
- Dogs: GI effects (anorexia, vomiting, diarrhea, abdominal distention)
- Dogs: CNS effects (lassitude, hyperactivity, behavioral changes, collapse)
- Dogs: Stiffness of limbs
- Dogs: Pruritus, exfoliative dermatitis, erythema of feet and mucocutaneous junctions/cheilitis
- Dogs: Polydipsia, swollen tongue
- Cats: Blepharospasm, periocular crusting, erythema
- Cats: Diarrhea
- Cats: Weight loss secondary to anorexia
藥物相互作用
- Vitamin A or other retinoids (etretinate, tretinoin) · May cause additive toxic effects.
- Cyclosporine · Isotretinoin may increase cyclosporine levels.
- Tetracyclines · Use with tetracyclines may increase the potential for the occurrence of pseudotumor cerebri (cerebral edema and increased CSF pressure).
監測
- Clinical efficacy
- Liver function tests (baseline and if signs appear)
- Serum triglycerides and cholesterol
- Dogs: Schirmer Tear tests (monthly, especially in older dogs to monitor for KCS)
- Cats: Body weight (monitor for anorexia-induced weight loss)
過量
In a review of 147 exposures reported to the ASPCA APCC (140 dogs, 7 cats), only 5 dogs showed clinical signs, most commonly **hypersalivation**. Cats showed no clinical signs. Because of the drug's potential adverse effects, **gut emptying** should be considered with acute overdoses when warranted. Monitor for GI upset and CNS signs.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。