アモキシシリン
Amoxicillin
Amoxicillin trihydrate
別名: Amoxil · Amoxi-Tabs · Amoxi-Drop · Amoxi-Mast · Trimox · Moxatag · Amoxibactin · Amoxycare · Amoxypen · Betamox · Bimoxyl · Clamoxyl · amoxycillin · p-hydroxyampicillin · BRL 2333
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 |
|---|---|---|---|---|---|
| Gram-positive infections | 10 mg/kg PO, IM, SC twice daily for at least 2 days after symptoms subside. | PO, IM, SC | q12h | At least 2 days after symptoms subside | 🌎 NA |
| Gram-negative infections | 20 mg/kg PO three times daily or IM, SC twice daily for at least 2 days after symptoms subside | PO, IM, SC | q8h (PO) or q12h (IM, SC) | At least 2 days after symptoms subside | 🌎 NA |
| Susceptible UTI's | 10-20 mg/kg PO q12h for 5-7 days. | PO | q12h | 5-7 days | 🌎 NA |
| Susceptible systemic infections (bacteremia/sepsis) | 22-30 mg/kg IV , IM, SC q8h for 7 days. | IV, IM, SC | q8h | 7 days | 🌎 NA |
| Susceptible orthopedic infections | 22-30 mg/kg IV , IM, SC, or PO q6-8h for 7-10 days. | IV, IM, SC, PO | q6-8h | 7-10 days | 🌎 NA |
| Lyme disease | 22 mg/kg PO q12h for 21-28 days | PO | q12h | 21-28 days | 🌎 NA |
| Susceptible urinary tract infections | 11 mg/kg PO q8h. | PO | q8h | — | 🌎 NA |
| Preventative therapy for repeated (>2 per 6 months) urinary tract Gram-positive bacterial infections | 20 mg/kg PO once daily before bedtime after the dog has urinated. | PO | q24h | — | 🌎 NA |
| Susceptible bacterial infections | 7 mg/kg | IM | q24h | — | 🌍 EU |
| Susceptible bacterial infections (depot preparations) | 15 mg/kg | IM | q48h | — | 🌍 EU |
| Susceptible bacterial infections | 10 mg/kg | PO | q8-12h | — | 🌍 EU |
| Bacterial cystitis | 11-15 mg/kg | PO | q8h | — | 🌍 EU |
- Preventative therapy for repeated (>2 per 6 months) urinary tract Gram-positive bacterial infections: Use only after effective treatment completed using full therapeutic doses.
- Susceptible bacterial infections (depot preparations): For depot preparations only
- Susceptible bacterial infections: Dose chosen will depend on site of infection, causal organism and severity of the disease.
- Bacterial cystitis: Evidence of a need for clavulanic acid is lacking even in infections with beta-lactamase producing bacteria.
猫
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Gram-positive infections | 10 mg/kg PO, IM, SC twice daily for at least 2 days after symptoms subside. | PO, IM, SC | q12h | At least 2 days after symptoms subside | 🌎 NA |
| Gram-negative infections | 20 mg/kg PO three times daily or IM, SC twice daily for at least 2 days after symptoms subside | PO, IM, SC | q8h (PO) or q12h (IM, SC) | At least 2 days after symptoms subside | 🌎 NA |
| Susceptible UTI's and soft tissue infections | 50 mg (total dose per cat) or 11-22 mg/kg PO once daily for 5-7 days. | PO | q24h | 5-7 days | 🌎 NA |
| Sepsis | 10-20 mg/kg IV , SC, or PO q12h for as long as necessary. | IV, SC, PO | q12h | As long as necessary | 🌎 NA |
| C. perfringens, bacterial overgrowth (GI) | 22 mg/kg PO once daily for 5 days | PO | q24h | 5 days | 🌎 NA |
| C. perfringens enterotoxicosis | 11-22 mg/kg PO two to three times daily for 7 days | PO | q8-12h | 7 days | 🌎 NA |
| H. pylori infections (triple therapy) | amoxicillin 20 mg/kg PO twice daily for 14 days; metronidazole 10-15 mg/kg PO twice daily; clarithromycin 7.5 mg/kg PO twice daily | PO | q12h | 14 days | 🌎 NA |
| Susceptible bacterial infections | 7 mg/kg | IM | q24h | — | 🌍 EU |
| Susceptible bacterial infections (depot preparations) | 15 mg/kg | IM | q48h | — | 🌍 EU |
| Susceptible bacterial infections | 10 mg/kg | PO | q8-12h | — | 🌍 EU |
| Bacterial cystitis | 11-15 mg/kg | PO | q8h | — | 🌍 EU |
- Sepsis: Generally treat for at least 2 days after all signs of infection are gone.
- H. pylori infections (triple therapy): Used in combination with metronidazole and clarithromycin.
- Susceptible bacterial infections (depot preparations): For depot preparations only
- Susceptible bacterial infections: Dose chosen will depend on site of infection, causal organism and severity of the disease.
- Bacterial cystitis: Evidence of a need for clavulanic acid is lacking even in infections with beta-lactamase producing bacteria.
小型哺乳類
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible infections (Hedgehogs) | 15 mg/kg IM or PO q12h | IM, PO | q12h | — | 🌎 NA |
- Susceptible infections (Hedgehogs): See contraindications regarding use in rabbits/rodents.
フェレット
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Eliminating Helicobacter gastritis infections (triple therapy) | Metronidazole 22 mg/kg, amoxicillin 22 mg/kg and bismuth subsalicylate (original Pepto-Bismol ®) 17.6 mg/kg PO. Give each 3 times daily for 3-4 weeks. | PO | q8h | 3-4 weeks | 🌎 NA |
| Eliminating Helicobacter gastritis infections (triple therapy) | Metronidazole 20 mg/kg PO q12h, amoxicillin 20 mg/kg PO q12h and bismuth subsalicylate 17.5 mg/kg PO q8h. Give 21 days. | PO | q12h | 21 days | 🌎 NA |
| Susceptible infections | 10-35 mg/kg PO or SC twice daily | PO, SC | q12h | — | 🌎 NA |
- Eliminating Helicobacter gastritis infections (triple therapy): Sucralfate and famotidine are also used. Fluids and assisted feeding should be continued.
鳥
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible infections | 125 mg/kg q12h PO. Mix oral solution to double strength to a final concentration of 125 mg/mL. | PO | q12h | — | 🌎 NA |
| Susceptible infections | 100 mg/kg q8h, IM, SC, PO | IM, SC, PO | q8h | — | 🌎 NA |
| Susceptible infections (Ratites) | 15-22 mg/kg PO twice daily; in drinking water: 250 mg/gallon for 3-5 days | PO, drinking water | q12h / continuous | 3-5 days | 🌎 NA |
爬虫類
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible infections (all species) | 22 mg/kg PO q12-24h | PO | q12-24h | — | 🌎 NA |
- Susceptible infections (all species): Not very useful unless used in combination with aminoglycosides
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Respiratory infections | 20-30 mg/kg PO q6h | PO | q6h | — | 🌎 NA |
| Susceptible infections (Foals - Amoxicillin Sodium) | 15-30 mg/kg IV or IM q6-8h | IV, IM | q6-8h | — | 🌎 NA |
| Susceptible infections (Foals - Amoxicillin trihydrate suspension) | 25-40 mg/kg PO q8h | PO | q8h | — | 🌎 NA |
| Susceptible infections (Foals - Amoxicillin/clavulanate) | 15-25 mg/kg IV q6-8h | IV | q6-8h | — | 🌎 NA |
牛
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| Susceptible infections | 6-10 mg/kg SC or IM q24h | SC, IM | q24h | — | 🌎 NA |
| Respiratory infections | 11 mg/kg IM or SC q12h | IM, SC | q12h | — | 🌎 NA |
| Susceptible infections (Calves - Amoxicillin trihydrate) | 7 mg/kg PO q8-12h | PO | q8-12h | — | 🌎 NA |
- Susceptible infections: Withdrawal time = 30 days
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
アモキシシリンは、獣医療において様々な細菌感染症の治療に広く処方される広域スペクトルアミノペニシリン系抗生物質です。
主な薬理学的特徴は以下の通りです：
- 抗菌スペクトル: 多くのグラム陽性好気性菌、一部のグラム陰性好気性菌（大腸菌、クレブシエラ、ヘモフィルスなど）、および多くの偏性嫌気性菌（クロストリジウム属を含む）に対して有効です。
- β-ラクタマーゼに対する感受性: アンピシリンと同様に、β-ラクタマーゼ産生菌（黄色ブドウ球菌など）によって不活化されます。この耐性を克服するため、しばしばクラブラン酸と併用されます。
- 臨床的有用性: 猫の膿瘍、感受性のある尿路感染症（UTI）、および軟部組織感染症に対する第一選択の経験的治療薬と見なされています。
- 薬物動態学的利点: アンピシリンと比較して、単胃動物における経口バイオアベイラビリティが著しく高く、同等用量で1.5〜3倍の血清中濃度を達成します。
作用機序
Amoxicillin is a time-dependent, bactericidal antibiotic that disrupts bacterial cell wall synthesis.
- Mechanism: The beta-lactam ring mimics the D-alanyl-D-alanine terminal of the peptidoglycan precursor.
- Pathway: Amoxicillin binds to specific penicillin-binding proteins (PBPs) (such as transpeptidases, carboxypeptidases, and endopeptidases) located on the inner surface of the bacterial cell membrane → inhibits the cross-linking of mucopeptide (peptidoglycan) chains → compromises the structural integrity of the cell wall → creates an osmotically unstable spheroplast → results in cell lysis and death.
- Efficacy: It is most effective against actively dividing and growing bacteria.
安全性・警告
禁忌
- Patients with a history of hypersensitivity to penicillins
- Oral administration in hindgut fermenters (rabbits, guinea pigs, chinchillas, hamsters) due to risk of fatal clostridial enterotoxemia
- Oral administration in patients with septicemia, shock, or grave illness (due to delayed/diminished GI absorption)
有害事象
- Gastrointestinal upset (anorexia, vomiting, diarrhea)
- Antibiotic-associated diarrhea and gut flora alteration
- Hypersensitivity reactions (rashes, fever, anaphylaxis)
- Eosinophilia, neutropenia, agranulocytosis, thrombocytopenia, leukopenia, anemias
- Lymphadenopathy
- Neurotoxicity (e.g., ataxia) at very high doses or prolonged use
- Elevated liver enzymes (rare)
- Tachypnea, dyspnea, edema, and tachycardia (reported in dogs)
注意事項
Species Warning: Never administer amoxicillin (or other penicillins) orally to rabbits, guinea pigs, chinchillas, or hamsters, as it can cause severe, often fatal, clostridial enterotoxemia.
- Cross-Reactivity: Use with caution in patients with documented hypersensitivity to other beta-lactam antibiotics (e.g., cephalosporins, carbapenems).
- Pregnancy: Crosses the placenta. Categorized as FDA Category B (human) and Class A (veterinary - probably safe), but should be used only when potential benefits outweigh risks.
- Laboratory Tests: May cause false-positive urine glucose determinations when using cupric sulfate solutions (e.g., Clinitest).
医薬品相互作用
Potential in vitro antagonism; concurrent use has historically been discouraged, though clinical significance is debated.
Amoxicillin may decrease the renal excretion of methotrexate, leading to increased levels and potential toxicity.
Competitively blocks the tubular secretion of penicillins, increasing serum levels and prolonging serum half-life.
In vitro inactivation of aminoglycosides by beta-lactams; may falsely decrease aminoglycoside serum concentrations if samples are stored prior to analysis.
Potential antagonism of bactericidal activity (bacteriostatic vs bactericidal)
Potential antagonism of bactericidal activity
Potential antagonism of bactericidal activity
Inactivation of aminoglycoside if mixed in the same syringe
Synergistic antimicrobial effect when used concurrently
監視
- Clinical efficacy (resolution of infection signs)
- Adverse effects (GI upset, signs of hypersensitivity)
薬物動態
半減期
吸収
Relatively stable in gastric acid. About 74-92% absorbed orally in monogastric animals. Food decreases the rate but not the extent of absorption. Serum levels are generally 1.5-3 times greater than ampicillin after equivalent oral doses.
分布
Volume of distribution is ~0.2 L/kg in dogs. Widely distributed to tissues including liver, lungs, muscle, bile, and ascitic/pleural/synovial fluids. Crosses into CSF when meninges are inflamed (10-60% of serum levels). Crosses the placenta. Protein binding is ~13% in dogs.
代謝
Some of the drug is metabolized by hydrolysis to inactive penicilloic acids.
消失
Eliminated primarily through renal mechanisms, principally by tubular secretion. Clearance is reportedly 1.9 mL/kg/min in dogs.
過剰投与
Acute oral penicillin overdoses are unlikely to cause significant problems other than gastrointestinal distress (vomiting, diarrhea, anorexia).
In humans, very high dosages of parenteral penicillins, especially in patients with compromised renal function, have induced CNS effects (e.g., seizures, ataxia). Treatment is generally supportive and symptomatic.
製品
製剤
- Oral tablets
- Oral chewable tablets
- Oral capsules
- Powder for oral suspension
- Intramammary infusion
動物用医薬品
- Amoxicillin Oral Tablets: 50 mg, 100 mg, 150 mg, 200 mg, & 400 mg (Amoxi-Tabs®)
- Amoxicillin Powder for Oral Suspension: 50 mg/mL after reconstitution (Amoxi-Drop®)
- Amoxicillin Intramammary Infusion: 62.5 mg/syringe (Amoxi-Mast®)
ヒト用医薬品
- Amoxicillin Oral Tablets (chewable): 125 mg, 200 mg, 250 mg, & 400 mg (Amoxil®)
- Amoxicillin Oral Tablets: 500 mg & 875 mg (Amoxil®)
- Amoxicillin Oral Capsules: 250 mg & 500 mg (Amoxil®)
- Amoxicillin Powder for Oral Suspension: 200 mg/5 mL, 250 mg/5 mL, 400 mg/5 mL (Amoxil®, Trimox®)
- Amoxicillin Oral Extended-Release Tablets: 775 mg (Moxatag®)
規制ステータス
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Capsules, tablets, and powder for oral suspension should be stored at room temperature (15-30°C) in tight containers. After reconstitution, the oral suspension should preferably be refrigerated (though not absolutely necessary) and any unused product discarded after 14 days.
飼主向け情報
- 投与方法: アモキシシリンは食事の有無にかかわらず投与できます。ただし、ペットが胃腸の不調（嘔吐や食欲不振）を起こした場合は、食事と一緒に与えることで改善する場合があります。
- 保管方法: 経口懸濁液（シロップ）を使用している場合は、冷蔵保存が望ましいですが、室温でも許容されます。調製後14日を過ぎた未使用の薬液は破棄してください。
- 治療の完了: ペットが完全に回復したように見えても、必ず獣医師の指示通りに処方された分を最後まで飲ませきってください。早期に投与を中止すると、耐性菌の発生につながる恐れがあります。
- 副作用: 軽度の下痢や嘔吐が起こることがあります。これらの症状が重度になった場合、またはアレルギー反応の兆候（顔の腫れ、蕁麻疹、呼吸困難など）に気づいた場合は、直ちに獣医師に連絡してください。
- 動物種に関する警告: ウサギ、モルモット、ハムスターなどの小動物には絶対にこの薬を与えないでください。これらの動物にとっては致命的となる可能性があります。
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。