頭孢噻肟
頭孢噻肟是一種**第三代注射用頭孢菌素**抗生素，對革蘭氏陽性菌和革蘭氏陰性菌均具有廣泛的抗菌活性。 主要臨床特徵包括： * **擴展的革蘭氏陰性菌覆蓋範圍**：對腸桿菌科（如克雷伯氏菌、大腸桿菌、沙門氏菌、變形桿菌）高度有效。 * **抗厭氧菌活性**：對許多厭氧菌有效，包括脆弱擬桿菌和梭狀芽孢桿菌屬。 * **中樞神經系統穿透力**：與第一代和多數第二代頭孢菌素不同，當腦膜發炎時，頭孢噻肟能在**腦脊髓液 (CSF)** 中達到治療濃度，使其成為治療細菌性腦膜炎和脊髓感染的重要選擇。 * **給藥方式**：因口服吸收不佳，必須經腸胃外途徑（靜脈、肌肉、皮下）給藥。靜脈注射應緩慢進行（超過3-5分鐘）以減少不良反應。 > **臨床要點**：雖然它對許多革蘭氏陰性需氧菌具有優異的活性，但對綠膿桿菌的療效不一，臨床效果通常不如預期。進行紙片擴散法藥敏試驗時，應使用30微克的頭孢噻肟紙片。
作用機制: 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.
各物種劑量
- 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
給藥途徑
禁忌症
- Patients with a documented history of hypersensitivity to cephalosporins
不良反應
- 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
藥物相互作用
- 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
監測
- Clinical efficacy (resolution of infection signs)
- Renal function parameters (BUN, creatinine, urinalysis) in compromised patients or those on concurrent nephrotoxic drugs
過量
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.
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