葉酸
Folic Acid
Pteroylglutamic acid
別名: Folvite · Deplin · Folate · Folacin · Vitamin B9 · Acidum folicum · Pteroylglutamic acid · Pteroylmonoglutamic acid · Vitamin B11
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Severe folate deficiency | 0.5-2 mg (total dose) PO once daily | PO | q24h | 1 month | 🌎 NA |
| Folate and cobalamin deficiency secondary to inflammatory bowel disease | 5 mg (total dose) PO once daily | PO | q24h | 1-6 months | 🌎 NA |
- Folate and cobalamin deficiency secondary to inflammatory bowel disease: Given with cyanocobalamin 750 micrograms parenterally once per month.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Severe folate deficiency | 0.5-2 mg (total dose) PO once daily | PO | q24h | 1 month | 🌎 NA |
| Folate deficiency secondary to exocrine pancreatic insufficiency | 400 micrograms (0.4 mg) PO once daily | PO | q24h | — | 🌎 NA |
| Long-term use of high dose trimethoprim/sulfa (for treating Nocardia) | 2 mg (total dose) PO once daily | PO | q24h | — | 🌎 NA |
| Adjunctive therapy in cats with inflammatory bowel disease | 0.5-1 mg PO q24h (once daily) | PO | q24h | 4-6 weeks | 🌎 NA |
- Adjunctive therapy in cats with inflammatory bowel disease: Given with cobalamin at 125-250 micrograms SC or IM once a week.
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Prolonged therapy with antifolate medications (e.g., trimethoprim, pyrimethamine) | 20-40 mg (total dose) PO per day | PO | q24h | — | 🌎 NA |
- Prolonged therapy with antifolate medications (e.g., trimethoprim, pyrimethamine): Pregnant mares should routinely receive folic acid supplementation during treatment with antifolates.
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
葉酸（ビタミンB9）は、核タンパク質合成および正常な赤血球形成に不可欠な重要な水溶性ビタミンです。
獣医学では、主に胃腸疾患に続発する葉酸欠乏症の治療に使用されます。
臨床的特徴と診断の有用性：
- 吸収部位： 葉酸は近位小腸で専ら吸収されますが、コバラミン（ビタミンB12）は遠位小腸で吸収されます。
- 診断指標： 血清葉酸およびコバラミンの測定は、腸疾患の局在化に役立ちます。葉酸の低下は近位小腸疾患を示唆します。
- 細菌異常増殖： 膵外分泌不全（EPI）または小腸内細菌異常増殖（SIBO）の犬では、腸内細菌が葉酸を合成するため、血清葉酸が上昇することがよくあります。
- 抗葉酸薬のレスキュー： ジヒドロ葉酸還元酵素阻害薬（トリメトプリム、ピリメタミンなど）の長期投与によって引き起こされる欠乏症の予防または治療にも使用されます。
作用機序
Folic acid is a precursor that must be enzymatically reduced to become biologically active.
Mechanism Pathway: Folic Acid → reduced by dihydrofolate reductase (DHFR) → Tetrahydrofolate (THF / 5-methyltetrahydrofolate).
- THF acts as a crucial coenzyme and methyl donor in the synthesis of purine and pyrimidine nucleotides.
- This pathway is absolutely necessary for DNA synthesis, cellular division, and the maintenance of normal erythropoiesis.
- Drugs like trimethoprim and methotrexate competitively inhibit DHFR, blocking this pathway and potentially causing megaloblastic anemia or leukopenia, which is why folic acid supplementation is used as a rescue therapy.
安全性・警告
禁忌
- Known intolerance or hypersensitivity to folic acid
- Undiagnosed anemias (folic acid therapy may mask the hematologic signs of pernicious anemia/cobalamin deficiency while neurologic damage progresses)
有害事象
- Hypersensitivity reactions (rare)
- Gastrointestinal effects (rare)
- CNS effects such as difficulty sleeping, excitement, or confusion (seen only at very high oral doses in humans, e.g., 15 mg/day)
注意事項
Important: Do not administer therapeutic doses of folic acid to dogs with enteropathies until baseline serum folate and cobalamin levels have been determined, as dogs may have increased, normal, or decreased folate levels depending on the specific disease process (e.g., bacterial overgrowth vs. malabsorption).
- Prolonged folic acid supplementation can potentially decrease serum cobalamin (B-12) levels.
- Folic acid is considered very safe during pregnancy (FDA Category A) and lactation. Requirements may actually increase in lactating animals.
医薬品相互作用
May delay the hematologic response to folic acid.
Inhibits dihydrofolate reductase; interferes with folic acid utilization.
Inhibits dihydrofolate reductase; interferes with folic acid utilization.
Inhibits dihydrofolate reductase; interferes with folic acid utilization.
Folic acid may decrease serum phenytoin levels, potentially requiring a dosage increase; increased seizure frequency can occur.
May increase the risk for folate deficiency.
May increase the risk for folate deficiency.
May increase the risk for folate deficiency.
May increase the risk for folate deficiency.
監視
- Serum folate and cobalamin levels (before and after treatment)
- Clinical signs associated with deficiency (e.g., chronic diarrhea, weight loss)
- CBC (baseline and ongoing if abnormal, to monitor for anemia)
薬物動態
吸収
Primarily absorbed in the proximal small intestine via carrier-mediated diffusion. Synthetic folic acid is nearly completely absorbed after oral administration, while folate in foodstuffs is about 50% bioavailable.
分布
Distributed widely throughout the body and stored in the liver. Erythrocyte and CSF levels can be significantly higher than serum levels. Undergoes enterohepatic recirculation.
代謝
Converted to its active form, tetrahydrofolic acid, principally in the liver and plasma.
消失
Excreted primarily in the urine either as metabolites or unchanged drug (when administered in excess of body requirements).
過剰投与
Folic acid is relatively non-toxic.
If an inadvertent overdose occurs, no specific treatment should be required. Excess drug is rapidly metabolized or excreted unchanged in the urine.
製品
製剤
- Tablets
- Injection
動物用医薬品
- None as sole ingredient products. (Available in various multivitamin combinations)
ヒト用医薬品
- Folic Acid Tablets: 0.4 mg, 0.8 mg (OTC); 1 mg, 7.5 mg, 15 mg (Rx)
- Deplin® (Pamlab)
- Folic Acid Injection: 5 mg/mL in 10 mL vials (Folvite®, generic) (Rx)
規制ステータス
規制データなし: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store tablets in well-closed containers below 40°C (104°F), preferably between 15-30°C; protect from light and moisture. Store injection protected from light below 40°C (104°F); do not freeze.
飼主向け情報
- 目的： 葉酸は、慢性腸疾患、膵臓の問題、または特定の抗生物質の長期使用によって引き起こされる欠乏症の治療に使用されるB群ビタミンです。
- 安全性： 非常に安全なサプリメントです。水溶性であるため、体内の余分な量は尿中に容易に排泄されます。
- 投与方法： 食事と一緒でも、空腹時でも与えることができます。獣医師の指示に注意深く従ってください。
- 長期ケア： ペットが慢性腸疾患や膵外分泌不全を患っている場合、健康を維持するために、生涯にわたるビタミンレベルのモニタリングと定期的な補充療法が必要になる場合があります。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。