ビタミンA / イソトレチノイン
ビタミンAおよびその誘導体（イソトレチノインやトレチノインなどのレチノイド）は、上皮組織の成長と分化に不可欠な脂溶性ビタミン/ホルモンです。獣医療では、主にビタミンA欠乏症や脂腺炎などの特定の皮膚疾患の治療に使用されます。 > **警告：** レチノイドには強い**催奇形性**があります。獣医師および飼い主は、特に妊娠中の女性への偶発的な曝露を防ぐため、細心の注意を払う必要があります。
作用機序: 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.
動物種別の用量
- 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.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Pregnant animals
- Breeding animals
- Patients at high risk for thrombosis
- Neonates
有害事象
- 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
薬物相互作用
- 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
モニタリング
- 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)
過量投与
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 の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。