維生素A / 異維A酸
維生素A及其衍生物（如異維A酸和維A酸）是脂溶性維生素/激素，對上皮組織的生長和分化至關重要。在獸醫學中，主要用於治療維生素A缺乏症以及某些皮膚病（如皮脂腺炎）。 > **警告：** 類維生素A具有高度**致畸性**。獸醫和寵物主人必須極度謹慎，以防止意外接觸，特別是孕婦。
作用機制: Acts as a nutritional fat-soluble hormone that regulates **gene expression**. Tretinoin (**all-trans retinoic acid**) is the acid form of vitamin A, and isotretinoin (**13-cis retinoic acid**) is an isomer of tretinoin. **Clinical Pearl:** They bind to intracellular **retinoic acid receptors (RARs)** and **retinoid X receptors (RXRs)** → modifying gene transcription → regulating epithelial cell growth, differentiation, and sebum production.
各物種劑量
- Antioxidant support, liver disease, or malabsorption (EPI) · 1.6-8.3 mg/kg or 100-400 IU/dog · PO · q24h · for the first 30 days, then as needed · Dose can be calculated by weight or given as a flat dose per dog.
- Antioxidant support or malabsorption · 1.6-8.3 mg/kg or 30 IU/cat · PO · q24h · for the first 30 days, then as needed · Frequency is implied as q24h based on dog dosing.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
給藥途徑
禁忌症
- Pregnant animals
- Breeding animals
- Patients at high risk for thrombosis
- Neonates
不良反應
- Teratogenicity (fetal malformations)
- Keratoconjunctivitis sicca (KCS / dry eye)
- Hepatotoxicity
- Hyperlipidaemia
- Hypercalcaemia (due to bone calcium loss with prolonged use)
- Skin redness and pigmentation
- Haematological abnormalities
- Nervous system changes
- Bone changes
- Thrombosis
- Anaphylactoid reactions
藥物相互作用
- Ciclosporin · Oral vitamin A may alter ciclosporin levels; requires close monitoring. · moderate
- Other topical drugs · Do not use topical vitamin A preparations simultaneously with other topical drugs. · moderate
- Vitamin A · May enhance vitamin A absorption, utilization, and storage. · minor
監測
- Signs of vitamin A toxicity
- Tear production (Schirmer Tear Test) for KCS
- Liver enzymes (ALT, AST, ALP)
- Serum calcium levels
- Serum triglycerides/lipids
- Ciclosporin levels (if used concurrently)
- Ciclosporin blood levels (if used concurrently)
- Coagulation parameters (in patients at risk for thrombosis)
- Liver enzymes (if treating hepatopathy)
過量
High doses or prolonged use can lead to severe **vitamin A toxicity**. Signs of toxicity include: - **Hepatotoxicity** - **Hyperlipidaemia** - **Hypercalcaemia** (due to promotion of calcium loss from bone) - Severe skin, haematological, and nervous system abnormalities. > **Treatment:** Discontinue the drug immediately and provide supportive care. Monitor liver enzymes and serum calcium.
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。