氰鈷胺（維生素B12）
氰鈷胺（維生素B12）是一種水溶性維生素，對維持正常細胞功能至關重要。 - **主要用途**：注射治療維生素B12缺乏症。 - **常見缺乏原因**：胰臟外分泌不足（EPI）、炎症性腸病（IBD）及其他吸收不良性胃腸道疾病。 - **物種特異性**： - **犬貓**：常因胃腸/胰臟疾病導致缺乏；巨型雪納瑞等品種可能有遺傳性吸收缺陷（Imerslund-Gräsbeck症候群）。 - **反芻動物**：缺乏通常繼發於飲食中**鈷**的缺乏，因為瘤胃微生物需要鈷來合成B12。 > **臨床重點**：與人類不同，犬貓缺乏TC1結合蛋白，因此在吸收不良時，其B12儲存量會在1-2個月內迅速耗盡，而人類則需要1-2年。
作用機制: 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.
各物種劑量
- 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
給藥途徑
禁忌症
- Hypersensitivity to cyanocobalamin or hydroxocobalamin
- Known hypersensitivity to cobalt or cobalamin
不良反應
- Pain at injection site (uncommon)
- Anaphylaxis (rarely reported in humans)
- Pain or stinging at the injection site
- Mild allergic reactions (rare)
藥物相互作用
- 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
監測
- 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
Cyanocobalamin is very safe. An inadvertent overdose given via SC or IM injection is unlikely to cause significant morbidity.
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