セファレキシン
セファレキシンは広く使用されている**第1世代セファロスポリン系**抗生物質です。グラム陽性菌、特に**Staphylococcus pseudintermedius**や**Staphylococcus aureus**に対して高い有効性を示し、獣医皮膚科、特に犬の膿皮症治療において中心的な役割を果たします。 * **抗菌スペクトル**: ほとんどのグラム陽性菌（レンサ球菌、ブドウ球菌）に優れた効果を示し、一部のグラム陰性菌（大腸菌、クレブシエラ、プロテウス・ミラビリス）にも有効です。 * **耐性**: 腸球菌、緑膿菌、メチシリン耐性ブドウ球菌（MRSA/MRSP）、およびBacteroides fragilisには通常無効です。 * **臨床的特徴**: セファレキシンは**時間依存性**の抗生物質であり、感染部位での薬物濃度が最小発育阻止濃度（MIC）を上回る時間が有効性を左右します。犬や猫では経口投与の忍容性が良好ですが、馬では経口バイオアベイラビリティが非常に低いです。
作用機序: 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.
動物種別の用量
- 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
投与経路
禁忌
- Known hypersensitivity to cephalosporins
- Patients with septicemia, shock, or grave illness (oral absorption is unreliable; parenteral routes preferred)
有害事象
- 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
薬物相互作用
- 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
モニタリング
- 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
過量投与
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 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。