頭孢羥氨苄
頭孢羥氨苄（Cefadroxil）是一種廣效的**第一代頭孢菌素**抗生素，主要在獸醫學中用於治療犬貓的皮膚、軟組織及泌尿生殖道敏感細菌感染。 在結構上與青黴素相似，頭孢菌素含有β-內醯胺環（beta-lactam ring），賦予其殺菌活性。第一代頭孢菌素如頭孢羥氨苄的特點是對大多數**革蘭氏陽性病原體**（包括假中間葡萄球菌、金黃色葡萄球菌和鏈球菌）具有極佳的抗菌活性，而對革蘭氏陰性菌（如大腸桿菌和奇異變形桿菌）的活性則較為有限且具變異性。 **臨床要點：** 頭孢羥氨苄的抗菌譜與另一種常見的第一代頭孢菌素——頭孢氨苄（Cephalexin）幾乎完全相同。然而，頭孢羥氨苄在犬貓體內的半衰期略長，這有時允許較低頻率的給藥（例如每天兩次而非每天三次），儘管其價格通常高於一般的頭孢氨苄。
作用機制: Cefadroxil is a **time-dependent, bactericidal** antibiotic. It exerts its effect by binding to specific **Penicillin-Binding Proteins (PBPs)** located inside the bacterial cell wall. * Binding to PBPs → **Inhibition of peptidoglycan cross-linking** (the structural backbone of the bacterial cell wall) → Weakening of the cell wall → Activation of bacterial autolysins → **Cell lysis and death**. Because it is a time-dependent antibiotic, maintaining serum drug concentrations above the Minimum Inhibitory Concentration (MIC) for the majority of the dosing interval is critical for clinical efficacy.
各物種劑量
- UTI · 22 mg/kg PO once daily · PO · q24h · 21 days or less
- Skin, pyoderma · 22-35 mg/kg PO q12h · PO · q12h · 3-30 days
- Systemic, orthopedic infections · 22 mg/kg PO q8-12h · PO · q8-12h · 30 days
- Susceptible gram-positive infections · 10 mg/kg q12h · PO · q12h
- Susceptible gram-negative infections · 30 mg/kg q8h · PO · q8h
- Susceptible infections · 22 mg/kg PO q12h · PO · q12h
- Susceptible infections · 15-20 mg/kg PO twice daily · PO · q12h
- Susceptible infections (skin, soft tissue, GU) · 22 mg/kg PO twice daily · PO · q12h · Skin/soft tissue: at least 3 days. GU: at least 7 days. Max 30 days. · Treat for at least 48 hours after animal is afebrile and asymptomatic. Reevaluate if no response after 3 days.
- Susceptible Staph infections · 30 mg/kg PO q12h · PO · q12h · May not be adequate dose for non-UTI's caused by E. coli.
- UTI · 11-22 mg/kg PO q12h · PO · q12h · 7-30 days
給藥途徑
禁忌症
- Known hypersensitivity to cephalosporins
- Septicemia, shock, or grave illness (oral absorption is unreliable; parenteral routes required)
不良反應
- Anorexia
- Vomiting
- Diarrhea
- Hypersensitivity reactions (rash, fever, eosinophilia, anaphylaxis)
- Antibiotic-associated diarrhea/superinfections
- Tachypnea (rare)
- Neurotoxicity (at high doses)
- Neutropenia/thrombocytopenia (rare, prolonged use)
- Hepatitis (rare)
- Nephrotoxicity (rare)
藥物相互作用
- Probenecid · Competitively blocks the tubular secretion of most cephalosporins, thereby increasing serum levels and serum half-lives.
監測
- Clinical efficacy (resolution of infection signs)
- Renal function (in patients with pre-existing diminished renal function)
過量
Acute oral cephalosporin overdoses are unlikely to cause significant problems other than **gastrointestinal distress** (vomiting, diarrhea, anorexia). Massive overdoses or prolonged use, particularly in patients with compromised kidney function, may theoretically lead to neurotoxicity, neutropenia, hepatitis, or nephrotoxicity. Treatment is generally supportive and symptomatic.
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