セフォタキシム
セフォタキシムは、グラム陽性菌およびグラム陰性菌の両方に対して広範な抗菌スペクトルを持つ**第3世代注射用セファロスポリン系**抗生物質です。 主な臨床的特徴： * **グラム陰性菌への拡張された抗菌力**：腸内細菌科（クレブシエラ、大腸菌、サルモネラ、プロテウスなど）に対して非常に有効です。 * **嫌気性菌への活性**：バクテロイデス・フラジリスやクロストリジウム属を含む多くの嫌気性菌に有効です。 * **中枢神経系への移行性**：第1世代およびほとんどの第2世代セファロスポリンとは異なり、髄膜に炎症がある場合、**脳脊髄液（CSF）**内で治療濃度に達するため、細菌性髄膜炎や脊髄感染症の治療に有用です。 * **投与方法**：経口ではほとんど吸収されないため、非経口（IV、IM、SC）で投与する必要があります。副作用を最小限に抑えるため、静脈内投与はゆっくり（3〜5分以上かけて）行う必要があります。 > **臨床のポイント**：多くのグラム陰性好気性菌に対して優れた活性を示しますが、緑膿菌に対する有効性は変動しやすく、臨床結果は期待外れになることがよくあります。感受性試験には30マイクログラムのセフォタキシムディスクを使用する必要があります。
作用機序: Cefotaxime is a **time-dependent, bactericidal** antibiotic. * **Mechanism**: It binds to specific **penicillin-binding proteins (PBPs)** located inside the bacterial cell wall → inhibits the third and final stage of bacterial cell wall peptidoglycan synthesis → leads to cell lysis and death mediated by bacterial cell wall autolytic enzymes (autolysins). * **Metabolism**: It is partially metabolized in the liver to **desacetylcefotaxime**, an active metabolite that works synergistically with the parent compound to enhance antibacterial activity.
動物種別の用量
- Soft tissue infections · 22 mg/kg IV, IM or SC q8h for 7 days or less or 50 mg/kg IV or IM q12h for 7 days or less · IV, IM, SC · q8h or q12h · 7 days or less
- Orthopedic infections · 20-40 mg/kg IV, IM or SC q6-8h for 7 days or less · IV, IM, SC · q6-8h · 7 days or less
- Severe bacteremia · 20-80 mg/kg IV q6h or 10-50 mg/kg IV q4-6h for as long as necessary · IV · q4-6h · As long as necessary
- Susceptible infections · 25-50 mg/kg IV, IM or SC q8h · IV, IM, SC · q8h
- Sepsis · 20-80 mg/kg IV, IM q8h · IV, IM · q8h
- CNS infections (spinal cord) · 25 mg-50 mg/kg IV, IM q8h · IV, IM · q8h
- Acute sepsis or serious susceptible infections · 40-50 mg/kg · IV/IM/SC · q8h · Until clinical resolution · Standard recommended dose.
- Susceptible infections · 10-20 mg/kg · IV/IM/SC · q12h · Until clinical resolution · Lower dose suggested by some authors to have good clinical efficacy.
- Susceptible infections (most birds) · 50-100 mg/kg IM three times a day · IM · TID · May be used with aminoglycosides, but nephrotoxicity may occur. Reconstituted vial good for 13 weeks if frozen.
- Bacterial infections, bacterial hepatitis · 75-100 mg/kg IM or IV q4-8h · IM, IV · q4-8h
投与経路
禁忌
- Patients with a documented history of hypersensitivity to cephalosporins
有害事象
- Pain at the IM injection site
- Thrombophlebitis (after IV administration)
- Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
- Antibiotic-associated diarrhea (alteration of gut flora)
- Sterile abscesses or local tissue reactions
- Rarely: Nephrotoxicity, neurotoxicity (at high doses), neutropenia, agranulocytosis, thrombocytopenia, hepatitis
薬物相互作用
- Aminoglycosides / Nephrotoxic drugs (e.g., amphotericin B) · Potential for additive nephrotoxicity. In vitro studies show synergistic antibacterial activity, but they must NOT be mixed in the same syringe or fluid bag.
- Probenecid · Competitively blocks the renal tubular secretion of cefotaxime, significantly increasing its serum levels and prolonging its elimination half-life.
- Oxytetracycline · Bacteriostatic agents may antagonize the bactericidal activity of cephalosporins. · moderate
- Erythromycin · Bacteriostatic agents may antagonize the bactericidal activity of cephalosporins. · moderate
- Aminoglycosides · Synergistic antibacterial effect, but do not mix in the same syringe due to chemical incompatibility. · minor
- Amphotericin B · Increased risk of nephrotoxicity. · major
- Furosemide · Loop diuretics may increase the risk of nephrotoxicity when used with cephalosporins. · major
モニタリング
- Clinical efficacy (resolution of infection signs)
- Renal function parameters (BUN, creatinine, urinalysis) in compromised patients or those on concurrent nephrotoxic drugs
過量投与
Acute cephalosporin overdoses are unlikely to cause significant life-threatening problems. However, massive overdoses may exacerbate adverse effects, potentially leading to **neurotoxicity** (seizures, encephalopathy), **nephrotoxicity**, or severe gastrointestinal upset. Treatment should consist of standard supportive care and monitoring.
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。