ピリドキシン (ビタミンB6)
**ピリドキシン（ビタミンB6）**は、多くの代謝プロセスに不可欠な水溶性ビタミンです。獣医学における主な特定の適応症は、イソニアジド（INH）またはクリミジン中毒の**解毒剤**として、またリポソーム化ドキソルビシン（**Doxil®**）に関連する皮膚毒性（手足症候群）を遅らせることです。 *臨床のポイント*：バランスの取れた市販のフードを食べている犬や猫で食事性の欠乏症が起こることは極めてまれですが、重度の胃腸疾患を持つ猫ではピリドキシンの必要量が増加する可能性があります。さらに、インビトロ研究では、ピリドキシンが猫の乳腺腫瘍の増殖を抑制できることが示されています。
作用機序: Pyridoxine is converted in erythrocytes to **pyridoxal phosphate** and, to a lesser extent, **pyridoxamine**, which act as vital coenzymes for protein, lipid, and carbohydrate utilization. * **Neurotransmitter Synthesis**: Required for the synthesis of **GABA** (gamma-aminobutyric acid) in the CNS, and the conversion of tryptophan → **serotonin** or niacin. * **Metabolic Pathways**: Essential for glycogen breakdown, heme synthesis, and the conversion of oxalate → glycine. * **Toxicity Antidote**: Acts as an antidote by directly enhancing the renal excretion of cycloserine and isoniazid.
動物種別の用量
- To replace pyridoxine antagonized by crimidine ingestion · 20 mg/kg · IV · Once
- Isoniazid (INH) toxicity · If quantity of INH ingested is known, give pyridoxine on a mg for mg (1:1) basis. If it is not known, give pyridoxine initially at 71 mg/kg as a 5-10% IV infusion over 30-60 minutes · IV · Once · Some sources say it can be given as an IV bolus. Do not use injectable B-complex vitamins.
- To replace pyridoxine antagonized by crimidine ingestion · 20 mg/kg · IV · Once
- To delay the development of cutaneous toxicity (PPES) associated with doxorubicin containing pegylated liposomes (Doxil®) · 50 mg · PO · q8h (three times daily) · During chemotherapy protocol period
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
- Documented hypersensitivity or sensitivity to pyridoxine
有害事象
- Paresthesias (reported in humans)
- Somnolence (reported in humans)
- Reduced serum folic acid levels
- Peripheral neuropathy (associated with massive overdoses)
薬物相互作用
- Chloramphenicol · May cause increased pyridoxine requirements
- Estrogens · May cause increased pyridoxine requirements
- Hydralazine · May cause increased pyridoxine requirements
- Immunosuppressants (e.g., azathioprine, chlorambucil, cyclophosphamide, corticosteroids) · May cause increased pyridoxine requirements
- Isoniazid · May cause increased pyridoxine requirements
- Penicillamine · May cause increased pyridoxine requirements
- Levodopa · Pyridoxine may reduce levodopa efficacy (no interaction when levodopa is used with carbidopa)
- Phenobarbital · High dose pyridoxine may decrease phenobarbital serum levels
- Phenytoin · High dose pyridoxine may decrease phenytoin serum concentration
モニタリング
- Efficacy for intended use
- Neurologic signs (gait, coordination) if on high doses
過量投与
> **Warning**: While single overdoses are generally not problematic unless massive, chronic high doses can cause severe neurologic toxicity. * **Massive Acute Overdose**: Laboratory animals given 3-4 grams/kg developed seizures and died. * **Chronic Overdose**: Dogs (Beagles) repeatedly given 3 gram oral daily doses developed uncoordinated gait and neurologic signs. Neuronal lesions were noted in sensory, dorsal root ganglia, and trigeminal ganglia. Signs generally resolved over a 2-month drug-free period.
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。