アモキシシリン・クラブラン酸
アモキシシリン・クラブラン酸（獣医療では商品名 **Clavamox®** としてよく知られています）は、非常に有効で広域スペクトルを持つ**配合アミノペニシリン**系抗生物質です。 * **抗菌スペクトルの拡大：** β-ラクタマーゼ阻害薬であるクラブラン酸を加えることで、アモキシシリンが酵素によって分解されるのを防ぎ、β-ラクタマーゼ産生菌（ブドウ球菌や大腸菌など）に対しても有効性を示します。 * **臨床用途：** 犬および猫の尿路感染症（UTI）、皮膚および軟部組織感染症、歯周病の治療薬としてFDAに承認されています。 * **経験的治療の第一選択：** 雌犬の細菌性膀胱炎に対する優れた第一選択薬であり、フルオロキノロン系と併用することで肝胆道系感染症にも適応されます。 * **制限事項：** クラブラン酸では阻害できないタイプIセファロスポリナーゼを産生することが多い**緑膿菌（Pseudomonas aeruginosa）**や**エンテロバクター属（Enterobacter）**には通常**無効**です。
作用機序: **Amoxicillin** is a time-dependent, bactericidal antibiotic that binds to **Penicillin-Binding Proteins (PBPs)** → inhibits bacterial cell wall peptidoglycan cross-linking → compromises cell wall integrity → cell lysis and death. **Clavulanic acid** acts as a "suicide inhibitor" by competitively and irreversibly binding to **beta-lactamase enzymes** (types II, III, IV, V, and staphylococcal penicillinases) → prevents the enzymatic destruction of amoxicillin → restores and expands the antimicrobial spectrum against resistant organisms. *Note: There is little synergistic activity against organisms already susceptible to amoxicillin alone.*
動物種別の用量
- Susceptible infections · 62.5 mg/cat · PO · twice daily · do not exceed 30 days
- Gram-positive infections · 10 mg/kg · PO · twice daily
- Gram-negative infections · 20 mg/kg · PO · three times daily
- Susceptible UTI's · 62.5 mg/cat (total dose) · PO · q12h · 10-30 days
- Susceptible skin, soft tissue infections · 62.5 mg/cat (total dose) or 10-20 mg/kg · PO · q12h · 5-7 days
- Susceptible sepsis, pneumonia · 10-20 mg/kg · PO · q8h · 7-10 days
- Susceptible infections · 10-20 mg/kg · PO · 2-3 times daily
- Susceptible infections · 50-100 mg/kg · PO · q6-8h
- Susceptible infections (Ratites) · 10-15 mg/kg · PO · twice daily
- Susceptible infections · 13.75 mg/kg · PO · twice daily · do not exceed 30 days
投与経路
禁忌
- Patients with a history of hypersensitivity to penicillins
- Small 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)
- Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
- Antibiotic-associated diarrhea and superinfections (due to altered gut flora)
- Neurotoxicity (e.g., ataxia in dogs) at very high doses or prolonged use
- Elevated liver enzymes (rare)
- Tachypnea, dyspnea, edema, and tachycardia (rarely reported in dogs)
薬物相互作用
- Bacteriostatic Antimicrobials (e.g., chloramphenicol, macrolides, tetracyclines, sulfonamides) · Theoretical in vitro antagonism; clinical importance is currently in doubt but historically not recommended to combine.
- Methotrexate · Amoxicillin may decrease the renal excretion of methotrexate, causing increased levels and potential toxic effects.
- Probenecid · Competitively blocks the tubular secretion of most penicillins, thereby increasing serum levels and serum half-lives.
- Aminoglycosides · In vitro inactivation can occur if mixed together; serum concentrations of aminoglycosides may be falsely decreased if stored prior to analysis.
モニタリング
- Clinical efficacy (resolution of infection signs)
- Adverse gastrointestinal signs (vomiting, diarrhea, anorexia)
過量投与
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 underlying renal disease, have induced Central Nervous System (CNS) effects. Treatment of oral overdose should be supportive and symptomatic.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。