頭孢西丁
頭孢西丁是一種**第二代注射用頭孢菌素**（嚴格來說屬於頭黴素類），在獸醫學中用於治療嚴重或混合性細菌感染。 主要藥理特點包括： * **抗厭氧菌效力**：與許多早期頭孢菌素不同，頭孢西丁對**厭氧菌**（包括脆弱擬桿菌 *Bacteroides fragilis*）具有極佳的抗菌效果。 * **革蘭氏陰性菌抗菌譜**：對許多可能對第一代藥物產生抗藥性的大腸桿菌 (*E. coli*)、克雷伯氏菌 (*Klebsiella*) 和變形桿菌 (*Proteus*) 菌株具有良好的活性。 * **革蘭氏陽性菌抗菌譜**：保留了對革蘭氏陽性球菌的活性，儘管在同等劑量下其效力略低於第一代頭孢菌素。 > **臨床要點**：由於其強大的抗厭氧菌抗菌譜，頭孢西丁經常被選用於治療混合感染，如吸入性肺炎、腸穿孔以及嚴重的軟組織感染或敗血症。
作用機制: Cefoxitin is a **bactericidal** antibiotic that works by inhibiting bacterial cell wall synthesis. * It covalently binds to specific **Penicillin-Binding Proteins (PBPs)** located inside the bacterial cell wall. * Binding to PBPs → **inhibits the transpeptidation enzyme** responsible for cross-linking peptidoglycan strands. * Lack of cross-linking → weakens the bacterial cell wall → leads to osmotic instability, cell lysis, and bacterial death. * As a cephamycin, cefoxitin is highly resistant to degradation by many **beta-lactamases**, particularly those produced by *Bacteroides* species.
各物種劑量
- Systemic infections · 25-30 mg/kg IV or IM q8h · IV/IM · q8h · Use as long as necessary to control initial infection, then switch to oral drugs
- Sepsis · 30 mg/kg IV q5h · IV · q5h
- Susceptible infections · 30 mg/kg IV q8h · IV · q8h
- Non-tuberculosis mycobacteria (NTM) - second line treatment · 30-40 mg/kg IV, IM or SC q6-8h · IV/IM/SC · q6-8h · Causes pain on injection with IM or SC
- Susceptible infections (Foals) · 20 mg/kg IV q4-6h · IV · q4-6h
- Mixed infections (e.g., aspiration pneumonia, bowel perforation) · 30 mg/kg SC q8h; 30 mg/kg IV q4-6h · SC/IV · q8h or q4-6h
- Sepsis · 30 mg/kg IV q5h · IV · q5h
- Soft tissue infections · 30 mg/kg SC q8h or 30 mg/kg IV q5h · SC/IV · q8h or q5h
- Bacteremia · 15-30 mg/kg IV, IM SC q6-8h · IV/IM/SC · q6-8h
- Orthopedic infections · 22 mg/kg IV, IM q6-8h · IV/IM · q6-8h · Use as long as necessary to control initial infection, then switch to oral drugs
給藥途徑
禁忌症
- Patients with a history of hypersensitivity to cephalosporins
- Use with extreme caution in patients documented to be hypersensitive to other beta-lactams (penicillins, carbapenems)
不良反應
- Hypersensitivity reactions (rashes, fever, eosinophilia, lymphadenopathy, anaphylaxis)
- Pain at the injection site (IM)
- Sterile abscesses or local tissue reactions
- Thrombophlebitis (IV administration)
- Antibiotic-associated diarrhea or altered gut flora
- Superinfections
- Nephrotoxicity (rare at clinical doses)
- Neurotoxicity, neutropenia, thrombocytopenia, hepatitis (associated with high doses or prolonged use)
藥物相互作用
- Aminoglycosides / Nephrotoxic Drugs · Potential for additive nephrotoxicity. While in vitro synergy exists against certain bacteria, they should not be mixed in the same syringe or fluid bag.
- Probenecid · Competitively blocks the tubular secretion of cefoxitin, thereby increasing serum levels and prolonging elimination half-lives.
監測
- Clinical efficacy (resolution of infection signs)
- Renal function (BUN, creatinine, urinalysis) in patients with diminished renal capacity
過量
Acute oral cephalosporin overdoses are unlikely to cause significant problems other than **gastrointestinal distress**. Massive parenteral overdoses or prolonged accumulation (especially in renal failure) may lead to: * Neurotoxicity (seizures) * Neutropenia or thrombocytopenia * Hepatitis * Nephrotoxicity (tubular necrosis) Treatment is supportive and symptomatic.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。