頭孢氨苄
頭孢氨苄是一種廣泛使用的**第一代頭孢菌素**抗生素。它對革蘭氏陽性菌具有極高的抗菌活性，特別是**假中間葡萄球菌 (Staphylococcus pseudintermedius)** 和 **金黃色葡萄球菌 (Staphylococcus aureus)**，使其成為獸醫皮膚科（尤其是犬膿皮症）的基石療法。 * **抗菌譜**：對大多數革蘭氏陽性病原體（鏈球菌、葡萄球菌）具有優異的覆蓋率，對部分革蘭氏陰性病原體（如大腸桿菌、克雷伯氏菌、奇異變形桿菌）具有不同程度的抗菌效果。 * **抗藥性**：通常對腸球菌、綠膿桿菌、耐甲氧西林葡萄球菌 (MRSA/MRSP) 和脆弱擬桿菌無效。 * **臨床要點**：頭孢氨苄是一種**時間依賴性**抗生素，這意味著其療效取決於藥物濃度在感染部位維持高於最低抑菌濃度 (MIC) 的時間。犬貓口服耐受性良好，但在馬的口服生物利用度極差。
作用機制: Cephalexin is a **bactericidal** antibiotic that disrupts bacterial cell wall synthesis. * **Mechanism**: It binds to specific enzymes known as **penicillin-binding proteins (PBPs)** (e.g., transpeptidases, carboxypeptidases) located on the inner surface of the bacterial cell membrane. * **Pathway**: Binding to PBPs → Inhibition of the final transpeptidation step of peptidoglycan synthesis → Formation of a defective, osmotically unstable cell wall (spheroplast) → **Cell lysis and death**. * Like other beta-lactams, it is most effective against actively dividing bacteria.
各物種劑量
- For superficial and deep pyoderma · 22-33 mg/kg PO two to three times daily · PO · q8-12h · 5-7 days beyond resolution
- For recurrent pyoderma · 22 mg/kg PO q12h (use at q8h for deep pyoderma) · PO · q8-12h · 5-7 days beyond resolution
- For superficial canine pyoderma · 30-40 mg/kg PO once daily (q24h) for 4 weeks. · PO · q24h · 4 weeks
- For pyoderma · 22-35 mg/kg PO q12h or 22 mg/kg PO q8h · PO · q8-12h · 5-7 days beyond resolution
- For respiratory infections · 20-40 mg/kg PO q8h · PO · q8h · 5-7 days beyond resolution
- For soft tissue infections · 30-50 mg/kg PO q12h · PO · q12h · 5-7 days beyond resolution
- For systemic infections · 25-60 mg/kg PO q8h · PO · q8h · 5-7 days beyond resolution
- For orthopedic infections · 22-30 mg/kg PO q6-8h for 28 days · PO · q6-8h · 28 days
- For pyometra/metritis · 10-30 mg/kg PO q8-12h · PO · q8-12h
- For UTI · 30-40 mg/kg PO q8h. · PO · q8h · 7-10 days for acute; up to 4-8 weeks for chronic/pyelonephritis
- For neonates · 10-30 mg/kg PO twice daily-three times daily · PO · q8-12h · Weak neonates should be given via stomach tube
給藥途徑
禁忌症
- Known hypersensitivity to cephalosporins
- Patients with septicemia, shock, or grave illness (oral absorption is unreliable; parenteral routes preferred)
不良反應
- Gastrointestinal upset (anorexia, vomiting, diarrhea)
- Hypersensitivity reactions (rashes, fever, eosinophilia, anaphylaxis)
- Salivation, tachypnea, and excitability (reported in dogs)
- Emesis and fever (reported in cats)
- Nephrotoxicity (rare)
- Toxic epidermal necrolysis (rarely reported in cats)
- Antibiotic-associated diarrhea or gut flora alteration
藥物相互作用
- Probenecid · Competitively blocks the tubular secretion of cephalosporins, thereby increasing serum levels and prolonging serum half-lives.
- Aminoglycosides · Increased risk of nephrotoxicity. Do not mix in the same syringe. · major
- Amphotericin B · Increased risk of nephrotoxicity. · major
- Loop diuretics (e.g., furosemide) · Increased risk of nephrotoxicity. · moderate
監測
- Clinical efficacy (resolution of clinical signs and negative cultures)
- Renal function (BUN, creatinine, urinalysis) in patients with pre-existing renal disease or those on concurrent nephrotoxic drugs
過量
Acute oral cephalosporin overdoses are unlikely to cause significant problems other than **gastrointestinal distress** (vomiting, diarrhea, anorexia). * **Severe Overdose**: Extremely high doses or very prolonged use has been associated with neurotoxicity, neutropenia, agranulocytosis, thrombocytopenia, hepatitis, interstitial nephritis, and tubular necrosis. * **Treatment**: Treatment is generally supportive and symptomatic. Emptying the gut may be considered for massive recent ingestions.
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。