ニトロフラントイン
Nitrofurantoin
Synthetic nitrofuran antibacterial
別名: Macrodantin · Macrobid · Furadantin · furadoninum · nitrofurantoinum · Nitrofurantoine
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 |
|---|---|---|---|---|---|
| Prevention of re-infections with gram-negative organisms | 4 mg/kg | PO | q24h | Long-term | 🌎 NA |
| Recurrent UTI (Conventional dose) | 4 mg/kg | PO | q8h | — | 🌎 NA |
| Recurrent UTI (Prophylactic dose) | 3-4 mg/kg | PO | q24h | — | 🌎 NA |
| Susceptible bacterial urinary tract infections | 4 mg/kg | PO | q6-8h | — | 🌎 NA |
| Susceptible bacterial urinary tract infections | 5 mg/kg | PO | q8h | — | 🌎 NA |
| Susceptible bacterial urinary tract infections | 4.4 mg/kg | PO | q8h | — | 🌎 NA |
| Urinary tract infections (lower UTI only) | 4.4-5 mg/kg | PO | q8h | As directed by culture and sensitivity | 🌍 EU |
- Prevention of re-infections with gram-negative organisms: Give once a day immediately before bedtime after the dog has urinated. Only use after extensive search for underlying cause and after effective treatment of existing UTI.
- Recurrent UTI (Prophylactic dose): Should be given at night after micturition and immediately before bedtime.
- Susceptible bacterial urinary tract infections: Listed as three times daily.
- Urinary tract infections (lower UTI only): For urinary tract infections only. Not for pyelonephritis.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible bacterial urinary tract infections | 5 mg/kg | PO | q8h | — | 🌎 NA |
| Recurrent UTI (Conventional dose) | 4 mg/kg | PO | q8h | — | 🌎 NA |
| Recurrent UTI (Prophylactic dose) | 3-4 mg/kg | PO | q24h | — | 🌎 NA |
| Susceptible bacterial urinary tract infections | 4 mg/kg | PO | q6-8h | — | 🌎 NA |
| Urinary tract infections (lower UTI only) | 4.4-5 mg/kg | PO | q8h | As directed by culture and sensitivity | 🌍 EU |
- Recurrent UTI (Prophylactic dose): Should be given at night after micturition and immediately before bedtime.
- Urinary tract infections (lower UTI only): For urinary tract infections only. Not for pyelonephritis.
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible urinary tract infections | 2.5-4.5 mg/kg | PO | q8h | — | 🌎 NA |
| Susceptible urinary tract infections | 10 mg/kg | PO | q24h | — | 🌎 NA |
- Susceptible urinary tract infections: Listed as three times daily.
- Susceptible urinary tract infections: Listed as daily.
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
ニトロフラントイン (Nitrofurantoin) は、主に尿路防腐剤/抗菌薬として使用される合成ニトロフラン系抗菌薬です。
- 部位特異的な有効性：尿中に急速に排泄されるため、下部尿路では高濃度に達しますが、全身の血流や組織では治療濃度に達しません。したがって、下部尿路感染症 (UTI) には非常に有効ですが、全身性感染症、腎盂腎炎（腎臓の感染症）、または腎周囲膿瘍には無効です。
- 抗菌スペクトル：大腸菌 (E. coli)、クレブシエラ (Klebsiella)、ブドウ球菌 (Staphylococcus)、腸球菌 (Enterococcus) など、多くのグラム陰性菌およびグラム陽性菌に対して有効です。緑膿菌 (Pseudomonas spp.) やほとんどのプロテウス属 (Proteus) には無効であることに注意が必要です。
- 臨床上のポイント：第一選択の抗生物質に対する耐性が増加しているため、ニトロフラントインは、特に耐性大腸菌や腸球菌によって引き起こされる多剤耐性下部尿路感染症のために温存されることがよくあります。
作用機序
Nitrofurantoin can be bacteriostatic or bactericidal depending on the concentration and organism susceptibility.
- Mechanism: Inside the bacterial cell, nitrofurantoin is reduced by bacterial flavoproteins to highly reactive intermediate compounds.
- Pathway: Reactive intermediates → attack bacterial ribosomal proteins and other macromolecules → inhibit protein synthesis, aerobic energy metabolism (specifically acetyl coenzyme A), DNA synthesis, RNA synthesis, and cell wall synthesis.
- Environmental Factor: It exhibits significantly greater antibacterial activity in acidic environments.
安全性・警告
禁忌
- Renal impairment (decreased efficacy and increased risk of systemic toxicity)
- Known hypersensitivity to nitrofurantoin
- Pregnant patients at term (risk of hemolytic anemia in neonates)
- Rats (high risk of neurotoxicity)
- Significant renal impairment (decreased excretion leads to toxic serum levels)
- Pregnancy (mutagenic properties)
- Pyelonephritis
- Systemic infections outside the urinary tract
- Food-producing animals
有害事象
- Gastrointestinal disturbances (vomiting, nausea, diarrhea)
- Hepatopathy (can be severe or chronic)
- Myasthenic-like effects (rare, reversible in dogs)
- Infertility in male dogs
- Peripheral neuropathy (rare)
- Hemolytic anemia (rare)
- Pneumonitis (rare)
- Emesis
- Diarrhoea
- Gastrointestinal bleeding
- Hepatotoxicity
- Peripheral neuritis (rare)
- Pulmonary complications (rare)
- Thrombocytopenia (at high doses)
- Anaemia (at high doses)
- Leucopenia (at high doses)
- Prolonged bleeding times (at high doses)
注意事項
Renal Function Warning: Do not use in patients with compromised renal function. The drug relies on renal excretion to reach the site of infection (the bladder); poor kidney function means the drug won't work for the UTI and will accumulate in the blood, causing toxicity.
- Hepatotoxicity: Can cause drug-induced hepatopathy. Monitor liver enzymes if adverse effects are suspected, especially during long-term prophylactic use.
- Reproductive Warning: May cause infertility in male dogs. Use with caution in breeding animals.
- Lab Interference: May cause false-positive urine glucose results if using cupric-sulfate solutions (e.g., Clinitest). May also cause decreases in blood glucose and increases in serum creatinine, bilirubin, and ALP.
医薬品相互作用
Nitrofurantoin may antagonize the antimicrobial activity of fluoroquinolones; concomitant use should be avoided.
May increase the oral bioavailability and absorption of nitrofurantoin.
May inhibit the oral absorption of nitrofurantoin.
May inhibit the renal excretion of nitrofurantoin, potentially increasing systemic toxicity and reducing its effectiveness in the urinary tract.
Delays gastric emptying time and increases absorption/bioavailability of nitrofurantoin
Delays gastric emptying time and increases absorption/bioavailability of nitrofurantoin
Antagonism of antibacterial efficacy
May increase the hyperkalaemic effects of spironolactone
Significantly decreases the antibacterial activity of nitrofurantoin
監視
- Clinical efficacy (resolution of UTI symptoms, negative urine cultures)
- Adverse effects (especially GI upset)
- Periodic liver function tests (especially with chronic/prophylactic therapy)
- Resolution of clinical signs of UTI
- Urine culture and sensitivity
- Renal function (BUN, Creatinine)
- Complete Blood Count (CBC) if used long-term or at high doses
- Liver enzymes
薬物動態
半減期
吸収
Rapidly absorbed from the GI tract. Presence of food enhances absorption. Macrocrystalline forms are absorbed more slowly, resulting in less GI upset and prolonged urine levels.
分布
Therapeutic levels in systemic circulation are not maintained due to rapid elimination. Approximately 20-60% is bound to serum proteins. Crosses the placenta; minimal quantities found in milk.
代謝
Some of the drug is metabolized, primarily in the liver.
消失
Rapidly eliminated. Approximately 40-50% is excreted into urine unchanged via both glomerular filtration and tubular secretion. Peak urine levels occur within 30 minutes of dosing.
過剰投与
Because the drug is rapidly absorbed and excreted, patients with normal renal function usually require little therapy for mild overdoses.
- Massive Overdose: If ingestion was recent, empty the gut using standard protocols (emesis/gastric lavage).
- Monitoring: Monitor closely for gastrointestinal distress, hepatotoxicity, and neurologic signs. Provide supportive care as needed.
製品
製剤
- Oral capsules (macrocrystals)
- Oral capsules (monohydrate/macrocrystals)
- 50 mg tablet
- 100 mg tablet
- 25 mg/5 ml oral suspension
ヒト用医薬品
- Nitrofurantoin Macrocrystals Oral Capsules: 25 mg, 50 mg & 100 mg (Macrodantin, generic)
- Nitrofurantoin Monohydrate/Macrocrystals Oral Capsules: 100 mg (Macrobid, generic)
- Nitrofurantoin Oral Suspension: 25 mg/5 mL (5 mg/mL) (Furadantin)
- Nitrofurantoin 50 mg tablets
- Nitrofurantoin 100 mg tablets
- Nitrofurantoin 25 mg/5 ml oral suspension
規制ステータス
Banned for use in food-producing animals (Annex IV / Table 2 substance).
Human POM used under the prescribing cascade. Banned in food-producing animals.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Store in tight containers at room temperature and protect from light. Do not freeze the oral suspension. Nitrofurantoin will decompose if it comes into contact with metals other than aluminum or stainless steel.
飼主向け情報
ニトロフラントインは、膀胱炎の治療に特化した抗生物質です。尿中に濃縮されて細菌を死滅させますが、体の他の部位の感染症には効果がありません。
- 食事と一緒に与える：この薬は必ず食事やおやつと一緒に与えてください。これにより、胃の不調（嘔吐）を大幅に減らし、薬の吸収を良くすることができます。
- タイミングが重要：ペットが1日1回の予防用量で服用している場合は、就寝直前、つまり夜の最後の排尿の直後に与えてください。これにより、薬が夜間ずっと膀胱内に留まり、細菌と戦うことができます。
- 副作用に注意：最も一般的な副作用は嘔吐です。嘔吐がひどい場合や続く場合は、獣医師にご相談ください。
- 肝臓に関する警告：まれに、この薬が肝臓に影響を与えることがあります。白目や歯茎が黄色くなる、ひどい無気力、食欲不振に気づいた場合は、すぐに獣医師に連絡してください。
- 最後まで飲み切る：ペットの具合が良くなったように見えても、感染症の再発や耐性菌の発生を防ぐため、処方された抗生物質は最後まで飲み切ってください。
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。