アンピシリン
Ampicillin
Ampicillin sodium, Ampicillin trihydrate
別名: Polyflex · Principen · Amfipen · Ampicare · aminobenzylpenicillin · ampicillinum anhydricum · anhydrous ampicillin · AY-6108 · BRL-1341 · NSC-528986 · P-50 · Ampicillin sodium · Aminopenicillin
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
監査済み v13 用量エビデンス
構造化された用量計算エビデンスSusceptible infections (extra-label)
認証済み獣医師の確認が必要
- q12h
NA
必ず考慮する臨床コンテキスト (3)
- ■ Because penicillins usually have minimal toxicity associated with their use, monitoring for efficacy is usually all that is required unless toxic signs develop. Serum levels and therapeutic drug monitoring are not routinely done with these agents.
- Ampicillin trihydrate (Polyflex®) powder for injection should be stored at or below 25°C (77°F), with excursions permitted up to 30°C (86°F). After reconstitution, it is stable for 3 months when refrigerated.
- Ampicillin sodium powder for injection should be stored at room temperature (15°C-30°C [59°F-86°F]). The drug is relatively unstable after reconstitution and should be used within 1 hour of reconstitution. As the concentration of the drug in solution increases, the stability of the drug decreases. Dextrose may also speed the destruction of the drug by acting as a catalyst in the hydrolysis of ampicillin.
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
アンピシリンは、広域スペクトルを持つ時間依存性の殺菌性アミノペニシリン系抗生物質です。
主な薬理学的特徴：
- 抗菌スペクトル： 多くのグラム陽性菌（ペニシリン感受性の腸球菌 E. faecium など）、嫌気性菌（Clostridium 属など）、および一部のグラム陰性好気性菌（E. coli、Klebsiella、Haemophilus、Proteus mirabilis）に対して有効です。
- 耐性： 天然ペニシリンと同様に、ベータ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やすいです。緑膿菌、セラチア、エンテロバクター、および非定型病原体（マイコプラズマ、リケッチア、真菌）には無効です。
- 臨床的有用性： 小動物における経口投与は、生体利用率がより優れたアモキシシリンにほぼ取って代わられていますが、注射用アンピシリンは依然として重要な治療薬です。
- 塩の形態：
- アンピシリンナトリウム： 水溶性が高く、静脈内（IV）投与に適しており、急速かつ高い血清中ピーク濃度をもたらします。
- アンピシリン三水和物： 筋肉内（IM）または皮下（SC）用の持続性製剤で、吸収が遅く、血清中ピーク濃度が低くなります（ナトリウム塩の約半分）。全身感染症で高い最小発育阻止濃度（MIC）が必要な場合には使用すべきではありません。
作用機序
Ampicillin is a beta-lactam antibiotic that exerts its bactericidal effect by interfering with bacterial cell wall synthesis.
- Mechanism: Ampicillin covalently binds to specific Penicillin-Binding Proteins (PBPs) (primarily transpeptidases) located inside the bacterial cell wall.
- Pathway: Binding to PBPs → inhibition of the final transpeptidation step of peptidoglycan cross-linking → weakening of the cell wall structure → activation of endogenous autolytic enzymes (autolysins) → osmotic lysis and bacterial cell death.
- Pharmacodynamics: Efficacy is time-dependent, meaning the free drug concentration must remain above the Minimum Inhibitory Concentration (MIC) for a significant portion of the dosing interval (typically >40-50% of the interval).
安全性・警告
禁忌
- Patients with a known hypersensitivity to penicillins
- Oral administration in patients with septicemia, shock, or grave illness (due to delayed/diminished GI absorption)
- Oral or parenteral use in small hindgut fermenters (rabbits, guinea pigs, chinchillas, hamsters) due to risk of fatal clostridial enterotoxemia
有害事象
- Gastrointestinal upset (anorexia, vomiting, diarrhea)
- Antibiotic-associated diarrhea and superinfections (alteration of gut flora)
- Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
- Neurotoxicity (ataxia, seizures) at very high doses or prolonged use
- Elevated liver enzymes (rare)
- Tachypnea, dyspnea, edema, and tachycardia (reported in dogs)
注意事項
Cross-Reactivity: Use cautiously in patients with documented hypersensitivity to other beta-lactam antibiotics (e.g., cephalosporins, carbapenems), as cross-reactivity can occur.
Species Warning: Severe, potentially fatal enteritis and clostridial enterotoxemia can occur if administered to rabbits, guinea pigs, chinchillas, or hamsters.
Laboratory Interference: May cause false-positive urine glucose determinations when using cupric sulfate solutions (e.g., Clinitest). Glucose oxidase tests are unaffected.
医薬品相互作用
Potential in vitro antagonism; clinical significance is debated but concurrent use is traditionally discouraged.
Ampicillin 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 half-life.
In vitro inactivation of aminoglycosides if mixed in the same syringe or fluid bag. May also occur in vivo in patients with severe renal failure.
Antagonism of bactericidal effect due to bacteriostatic action
Antagonism of bactericidal effect due to bacteriostatic action
Antagonism of bactericidal effect due to bacteriostatic action
In vitro inactivation if mixed in the same syringe; however, exhibits synergistic antimicrobial effects when used concurrently in vivo
監視
- Clinical efficacy (resolution of infection signs)
- Adverse effects (GI signs, hypersensitivity reactions)
- Therapeutic drug monitoring is not routinely required due to the wide therapeutic index
薬物動態
半減期
吸収
Relatively stable in gastric acid. Oral absorption is 30-55% in monogastric animals on an empty stomach; food decreases the rate and extent of absorption. Parenteral trihydrate salt achieves serum levels approximately 1/2 those of a comparable dose of the sodium salt.
分布
Widely distributed to many tissues (liver, lungs, muscle, bile, ascitic/pleural/synovial fluids). Volume of distribution is ~0.3 L/kg in dogs, 0.167 L/kg in cats, and 0.16-0.5 L/kg in cattle. Crosses inflamed meninges (10-60% of serum levels). Low levels in aqueous humor, tears, sweat, saliva, and milk. Crosses the placenta. Approximately 20% bound to plasma proteins.
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. Excreted in the urine.
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, particularly in patients with underlying renal disease, have induced CNS effects (e.g., seizures, ataxia). Treatment is generally supportive and symptomatic.
製品
製剤
- Powder for injection (Ampicillin sodium)
- Powder for injection suspension (Ampicillin trihydrate)
- Oral capsules
- Powder for oral suspension
動物用医薬品
- Ampicillin Trihydrate Injection Powder for Suspension: 10 g and 25 g vials (Polyflex)
ヒト用医薬品
- Ampicillin Sodium Powder for Injection: 250 mg, 500 mg, 1 g, 2 g vials
- Ampicillin Oral Capsules (as trihydrate): 250 mg, 500 mg (Principen)
- Ampicillin Powder for Oral Suspension (as trihydrate): 125 mg/5 mL, 250 mg/5 mL (Principen)
規制ステータス
POM-V classification
POM-V (Prescription Only Medicine - Veterinarian)
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Capsules and powder for oral suspension: Store at room temperature (15-30°C). Reconstituted oral suspension: Stable for 14 days refrigerated (2-8°C) or 7 days at room temperature. Ampicillin trihydrate for injection (Polyflex): Stable for 3 months refrigerated. Ampicillin sodium for injection: Relatively unstable after reconstitution; generally use within 1 hour. Stability decreases as concentration increases. Dextrose speeds destruction. At ≤30 mg/mL in sterile water or 0.9% NaCl, stable up to 48 hours at 4°C.
飼主向け情報
- 投与方法： 獣医師からの特別な指示がない限り、適切な吸収を確保するため、この薬は空腹時（食事の少なくとも1時間前または2時間後）に経口投与してください。
- 保管方法： 経口懸濁液は冷蔵庫で保管し、14日経過した未使用の薬液は破棄してください。室温で保管した場合は、7日後に破棄してください。
- 副作用： 軽度の胃腸の不調（嘔吐、下痢、食欲低下）が起こる場合があります。これらの症状が重度であるか持続する場合は、獣医師に連絡してください。
- アレルギー反応： 顔の腫れ、じんましん、発疹、呼吸困難などのアレルギー反応の兆候に注意してください。これらが現れた場合は、直ちに獣医師の診察を受けてください。
- 治療の完了： ペットの体調が良くなったように見えても、耐性菌の発生を防ぐため、必ず指示通りに処方された薬を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。