シアノコバラミン（ビタミンB12）
シアノコバラミン（ビタミンB12）は、正常な細胞機能に不可欠な水溶性ビタミンです。 - **主な用途**: ビタミンB12欠乏症の注射治療。 - **欠乏の一般的な原因**: 膵外分泌不全（EPI）、炎症性腸疾患（IBD）、その他の吸収不良性消化管疾患。 - **種特異性**: - **犬と猫**: 消化管/膵臓疾患に続発する欠乏症が多く見られます。ジャイアント・シュナウザーなどの犬種では、遺伝的な吸収障害（イメルスルンド・グラスベック症候群）を持つ場合があります。 - **反芻動物**: 第一胃の微生物がB12を合成するためにコバルトを必要とするため、食事中のコバルト欠乏に続発することがよくあります。 > **臨床のポイント**: 人間とは異なり、犬や猫はTC1結合タンパク質を持たないため、吸収不良の状態ではわずか1〜2ヶ月でB12の貯蔵が急速に枯渇します（人間は1〜2年かかります）。
作用機序: Vitamin B12 acts as a crucial coenzyme for two major enzymatic pathways: 1. **Methylmalonyl-CoA mutase**: Converts methylmalonyl-CoA → succinyl-CoA. (Deficiency leads to methylmalonic acidemia/aciduria). 2. **Methionine synthase**: Catalyzes the remethylation of homocysteine → methionine, which is intimately linked with **folate** metabolism. - Required for normal cell growth, nucleoprotein and myelin synthesis, amino acid metabolism, and erythropoiesis. - **Note**: B12 deficiency can cause a functional folate deficiency. Unlike humans, macrocytic anemias do not appear to be a significant component of cobalamin deficiency in dogs or cats.
動物種別の用量
- Treatment of vitamin B12 deficiency associated with cobalt deficiency (Lambs) · 100 micrograms (total dose) · injection · once weekly
- Treatment of vitamin B12 deficiency associated with cobalt deficiency (Adult sheep) · 300 micrograms (total dose) · injection · once weekly
- Treatment of vitamin B12 deficiency associated with cobalt deficiency · 0.2-0.4 mL of a 5000 micrograms/mL injection (1000-2000 micrograms) · IM or SC · weekly intervals if necessary
- Cobalamin deficiency in cats with IBD · 250-500 micrograms (total dose per cat) · SC · once per week for 6 weeks, then every 1-2 months
- Adjunctive treatment of idiopathic hepatic lipidosis · 250 micrograms (total dose) · SC · once per week · 6 weeks · Recheck serum B12 level in one to two weeks after cessation of treatment as some cats may need repeated administration.
- Cobalamin deficiency associated with GI disease · 150-250 micrograms (total dose) · SC · once weekly for 6 weeks, then every 14 days for 6 weeks, then one dose 30 days later · Initial 16-week protocol · Based on body size. Recheck serum cobalamin concentration one month after last dose.
- Cobalamin deficiency associated with exocrine pancreatic insufficiency · 100-250 micrograms (total dose) · SC · once weekly · Periodically assess cobalamin and folate levels.
- Treatment of vitamin B12 deficiency associated with cobalt deficiency · 0.2-0.4 mL of a 5000 micrograms/mL injection (1000-2000 micrograms) · IM or SC · weekly intervals if necessary
投与経路
禁忌
- Hypersensitivity to cyanocobalamin or hydroxocobalamin
- Known hypersensitivity to cobalt or cobalamin
有害事象
- Pain at injection site (uncommon)
- Anaphylaxis (rarely reported in humans)
- Pain or stinging at the injection site
- Mild allergic reactions (rare)
薬物相互作用
- Antibiotics · Concurrent use can cause falsely low serum or red blood cell cobalamin values if a microbiologic method assay is used.
- Omeprazole · May decrease oral absorption of Vitamin B12 by altering gastric pH · minor
モニタリング
- Serum cobalamin levels
- Serum folate status (both before and after treatment)
- Clinical signs associated with deficiency (weight loss, poor haircoat, vomiting, diarrhea)
- CBC (baseline and ongoing if abnormal)
- Serum cobalamin (Vitamin B12) levels
- Serum folate levels
- Clinical signs of gastrointestinal disease (weight gain, fecal consistency)
過量投与
Cyanocobalamin is very safe. An inadvertent overdose given via SC or IM injection is unlikely to cause significant morbidity.
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。