頭孢氨苄
Cephalexin
Cephalexin monohydrate
別名: Keflex · Ceporex · Cefalexina · Cefaseptin · Cephacare · Cephorum · Rilexine · Therios · Tsefalen · cefalexinum · 66873 · Cephalexin
由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本
經審核的 v13 劑量證據
結構化劑量計算證據Susceptible infections (extra-label)
- q8-12h
NA
必須同時考慮的臨床上下文 (3)
- ■ Therapeutic drug monitoring is not routinely done with these agents.
- ■ This medicine can be given with or without food, but gastrointestinal side effects might be prevented if given with food.
- Cephalexin tablets, chewable tablets, capsules, and powder for oral suspension should be stored at room temperature (15°C-30°C; 59°F-86°F) in tight containers. After reconstitution, the oral suspension is stable for 2 weeks when refrigerated.
劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。
概覽
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.
安全性與警告
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
注意事項
Hypersensitivity Cross-Reactivity: Use with caution in patients with documented hypersensitivity to other beta-lactam antibiotics (e.g., penicillins, carbapenems), as cross-reactivity can occur.
- Renal Impairment: Use cautiously and consider dose reduction in patients with renal dysfunction or those receiving concurrent nephrotoxic drugs.
- Critically Ill Patients: Do not use oral systemic antibiotics in patients with shock or septicemia due to delayed or diminished GI absorption.
- Laboratory Interference: May cause false-positive urine glucose tests (with cupric sulfate solutions like Clinitest) and falsely elevated serum/urine creatinine (with Jaffe reaction).
藥物相互作用
Competitively blocks the tubular secretion of cephalosporins, thereby increasing serum levels and prolonging serum half-lives.
Increased risk of nephrotoxicity. Do not mix in the same syringe.
Increased risk of nephrotoxicity.
Increased risk of nephrotoxicity.
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
藥物動力學
半衰期
吸收
Rapidly and completely absorbed after oral administration. Bioavailability is approximately 75% in dogs and cats. Food has little impact on absorption. In horses, oral bioavailability is very low (approx. 5%).
分佈
Widely distributed into most body tissues and fluids. Crosses the placenta and is distributed into maternal milk in small amounts.
代謝
Undergoes minimal hepatic metabolism.
排除
Primarily excreted unchanged in the urine via glomerular filtration and tubular secretion.
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.
可用產品
劑型
- Oral capsules
- Oral tablets
- Powder for oral suspension
- Injectable suspension (available outside the USA)
獸醫用
- None approved in the USA (injectable forms available internationally)
人用標示
- Cephalexin Oral Capsules: 250 mg, 333 mg, 500 mg & 750 mg (Keflex, generic)
- Cephalexin Oral Tablets: 250 mg & 500 mg (Keflex, generic)
- Cephalexin Powder for Oral Suspension: 125 mg/5mL & 250 mg/5 mL (Keflex, generic)
各地核准狀態
POM-V classification
POM-V classification
暫無法規資料: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
儲存與穩定性
Store tablets, capsules, and powder for oral suspension at room temperature (15-30°C) in tight containers. After reconstitution, the oral suspension is stable for 2 weeks.
飼主須知
頭孢氨苄 (Cephalexin) 是一種常開立的抗生素，用於治療細菌感染，特別是皮膚感染（膿皮症）。
- 給藥方式：可隨餐或空腹給予。如果您的寵物在服藥後嘔吐或感到不適，請嘗試將藥物與少量食物或零食一起餵食。
- 完成療程：即使您的寵物看起來已經完全康復，也必須按照獸醫師的指示完成整個療程。提早停藥可能會導致細菌產生抗藥性。
- 過敏反應：雖然罕見，但可能會發生過敏反應。如果您發現寵物有臉部腫脹、蕁麻疹、嚴重搔癢、突然腹瀉或呼吸困難，請立即聯繫您的獸醫師。
- 儲存方式：膠囊和錠劑請存放於室溫。如果您使用的是懸浮液（藥水），請遵循瓶身上的儲存指示（通常混合後可穩定保存 14 天）。
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