リファンピシン
Rifampin
Rifampicin (semi-synthetic zwitterion derivative of rifamycin B)
別名: Rifadin · Rimactane · Ba-41166/E · L-5103 · NSC-113926 · rifaldazine · rifampicinum · rifamycin AMP · Rifampin
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 |
|---|---|---|---|---|---|
| Combination therapy of atypical Mycobacteria infections; treatment of resistant Staph endocarditis | 10-20 mg/kg PO q8-12h | PO | q8-12h | — | 🌎 NA |
| Alternate treatment for scarred pyogranulomatous pyoderma | 5-10 mg/kg PO q24h | PO | q24h | 4-8 weeks | 🌎 NA |
| Actinomycosis | 10-20 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| Susceptible infections (e.g., mycobacteriosis, resistant staphylococcal pyoderma, ehrlichiosis) | 10-15 mg/kg | PO | q24h | Duration depends on the specific infection being treated | 🌍 EU |
- Combination therapy of atypical Mycobacteria infections; treatment of resistant Staph endocarditis: In combination with amoxicillin/clavulanate or trimethoprim/sulfa
- Alternate treatment for scarred pyogranulomatous pyoderma: Must be used with another antibiotic to reduce risk for resistance development (e.g., cephalexin or a potentiated sulfonamide). Monitor CBC, liver screens, and UA every 2 to 3 weeks.
- Susceptible infections (e.g., mycobacteriosis, resistant staphylococcal pyoderma, ehrlichiosis): Must be used in combination with other antimicrobial drugs to prevent the emergence of resistant organisms.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible infections (e.g., mycobacteriosis, Rhodococcus equi, chlamydiosis, bartonellosis) | 10-15 mg/kg | PO | q24h | Duration depends on the specific infection being treated | 🌍 EU |
- Susceptible infections (e.g., mycobacteriosis, Rhodococcus equi, chlamydiosis, bartonellosis): Must be used in combination with other antimicrobial drugs to prevent the emergence of resistant organisms.
鳥
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Treatment of mycobacteriosis | 45 mg/kg PO once daily | PO | q24h | — | 🌎 NA |
- Treatment of mycobacteriosis: In combination with ethambutol (30 mg/kg PO once daily) and one of the following: clofazimine (6 mg/kg PO once daily) or isoniazid (30 mg/kg PO once daily).
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Treatment of Rhodococcus equi (C. equi) infections in foals | 5 mg/kg PO two times daily | PO | q12h | — | 🌎 NA |
| Treatment of Rhodococcus equi (C. equi) infections in foals | 5 mg/kg PO two times daily or 10 mg/kg PO once daily | PO | q12h or q24h | 4-9 weeks | 🌎 NA |
| Treatment of proliferative enteropathy caused by Lawsonia intracellularis in foals | 10 mg/kg PO once daily | PO | q24h | minimum of 21 days | 🌎 NA |
- Treatment of Rhodococcus equi (C. equi) infections in foals: With erythromycin 15-25 mg/kg, PO q12-24h. Clarithromycin may be superior due to erythromycin side effects.
- Treatment of Rhodococcus equi (C. equi) infections in foals: With erythromycin 25 mg/kg, PO q6-8h.
- Treatment of proliferative enteropathy caused by Lawsonia intracellularis in foals: In combination with erythromycin estolate (25 mg/kg PO q6-8h)
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
リファンピシンは、リファマイシン系に属する高脂溶性の半合成抗菌薬です。獣医学において、深部の細胞内感染症、特に子馬のロドコッカス・エクイ（Rhodococcus equi）感染症の治療における中心的な薬剤です。
乾酪化物、骨、膿瘍、マクロファージに浸透する優れた能力を持つため、マイコバクテリウム属、黄色ブドウ球菌、ローソニア・イントラセルラリスなどの細胞内病原体に対して非常に有効です。高濃度では、ある程度の抗真菌および抗ウイルス活性も示します。
臨床上のポイント： リファンピシンは絶対に単独療法として使用してはなりません。細菌は単一のステップの突然変異により急速に耐性を獲得します。常に他の抗菌薬（馬の場合はエリスロマイシンやクラリスロマイシンなどのマクロライド系、犬の場合はセファロスポリン系やサルファ剤など）と併用して処方されます。
作用機序
Rifampin can be bactericidal or bacteriostatic depending on the concentration and the susceptibility of the target organism.
- Target: It binds strongly to the beta subunit of bacterial DNA-dependent RNA polymerase.
- Pathway: Binding inhibits the enzyme → suppresses the initiation of chain formation for RNA synthesis → halts bacterial protein production → cell death.
- Selectivity: Rifampin is highly selective for bacterial enzymes and does not inhibit mammalian RNA polymerase, providing a wide margin of safety for the host.
安全性・警告
禁忌
- Hypersensitivity to rifampin or other rifamycins
- Use with extreme caution in patients with preexisting hepatic dysfunction
- Pregnancy (teratogenic at high doses)
- Pre-existing liver disease or hepatic dysfunction
有害事象
- Red-orange discoloration of bodily fluids (urine, tears, sweat, saliva)
- Gastrointestinal distress (anorexia, vomiting, diarrhea)
- Elevated liver enzymes and potential hepatotoxicity
- Rashes and erythema (noted in cats and humans)
- In horses (especially with macrolides): mild diarrhea to severe enterocolitis, hyperthermia, and acute respiratory distress
- Intravenous use in horses (rare): CNS depression, sweating, hemolysis, anorexia
- Elevated serum hepatic enzymes
- Clinical hepatitis
- Orange-red discoloration of urine, saliva, tears, and feces
- Gastrointestinal upset (anorexia, vomiting, diarrhea)
注意事項
Use with caution in patients with preexisting hepatic dysfunction; dosage reduction may be necessary. Never use as a monotherapy due to the rapid development of bacterial resistance. Rifampin is a potent inducer of hepatic microsomal enzymes, which can significantly alter the metabolism of concurrently administered drugs. It is excreted in maternal milk; use with caution in nursing veterinary patients. May cause false-positive BSP (bromosulfophthalein) test results and interfere with microbiologic assays of serum folate and vitamin B12.
医薬品相互作用
In vitro antagonism has been reported; concurrent use should be avoided.
Decreased serum levels and shortened half-life due to hepatic microsomal enzyme induction by rifampin.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Decreased serum levels and shortened half-life due to hepatic enzyme induction.
Increased rate of metabolism of theophylline due to hepatic enzyme induction.
Increased rate of metabolism of itraconazole due to hepatic enzyme induction, leading to subtherapeutic antifungal levels.
監視
- Clinical efficacy and resolution of infection
- Liver function tests (especially with long-term therapy)
- Chest radiographs and plasma fibrinogen levels (prognostic indicators for C. equi infections in foals after 1 week of therapy)
- Baseline and periodic serum hepatic enzyme levels (ALT, AST, ALP, Bilirubin)
- Clinical signs of hepatitis (icterus, anorexia, vomiting, lethargy)
薬物動態
半減期
吸収
Relatively well absorbed from the GI tract. Oral bioavailability is about 40-70% in horses and 37% in adult sheep. Concurrent food administration may delay and slightly reduce peak plasma levels.
分布
Very lipophilic. Readily penetrates most body tissues (including bone and prostate), cells, and fluids (including CSF). Uniquely penetrates abscesses and caseous material. 70-90% bound to serum proteins. Distributes into milk and crosses the placenta. Volume of distribution is ~0.9 L/kg in horses and 1.3 L/kg in sheep.
代謝
Metabolized in the liver to a deacetylated form that retains antibacterial activity. Rifampin induces hepatic microsomal enzymes, meaning elimination rates may increase over time with repeated dosing (auto-induction).
消失
Both the active metabolite and unchanged drug are excreted primarily in the bile, but up to 30% may be excreted in the urine. The parent drug undergoes substantial enterohepatic recirculation, but the metabolite does not.
過剰投与
Clinical signs of oral rifampin overdose are generally extensions of its adverse effects, including gastrointestinal distress, orange-red coloring of fluids, and skin erythema (noted particularly in cats).
Massive overdoses carry a significant risk of hepatotoxicity. Dogs may exhibit central nervous system depression.
Treatment:
- Empty the gut following standard decontamination protocols for massive oral overdosage.
- Monitor liver enzymes closely.
- Initiate supportive treatment as necessary.
製品
製剤
- Oral capsules
- Lyophilized powder for injection
- 150 mg capsule
- 300 mg capsule
- 20 mg/ml syrup
ヒト用医薬品
- Rifampin Oral Capsules: 150 mg & 300 mg (Rifadin®, Rimactane®, generic)
- Rifampin Lyophilized Powder for Injection Solution: 600 mg (Rifadin®, generic)
- Rifadin 150 mg capsules
- Rifadin 300 mg capsules
- Rifadin 20 mg/ml syrup
- Rimactane capsules
規制ステータス
Human authorized products used under the prescribing cascade. Rifamycins are critically important antimicrobials.
POM (Prescription Only Medicine). Used under the cascade.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Rifampin capsules should be stored in tight, light-resistant containers, preferably at room temperature (15-30°C).
飼主向け情報
- 無害な変色： この薬により、ペットの尿、涙、汗、唾液が赤オレンジ色になることがあります。これは完全に正常で無害ですが、布地、カーペット、または明るい色の毛に永久的なシミを残す可能性があることに注意してください。
- 投与方法： 最もよく吸収させるために、この薬は空腹時に与えてください。胃の不調を引き起こす場合は、少量のおやつと一緒に与えてもかまいません。
- 併用療法： リファンピシンはほとんどの場合、別の抗生物質と一緒に処方されます。両方の薬を指示通りに正確に与え、全コースを完了することが重要です。細菌がすぐにリファンピシンに対する耐性を持つ可能性があるため、決して途中でやめないでください。
- 注意すべき症状： 重度の下痢、食欲不振、極度の無気力、または目や歯茎の黄ばみ（黄疸）に気づいた場合は、肝臓への負担の兆候である可能性があるため、獣医師に連絡してください。
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。