氧四環黴素（眼用）
**氧四環黴素**是一種屬於四環黴素類的廣效抑菌抗生素。 * **獸醫應用：** 在獸醫眼科中，最常用於治療貓的披衣菌（*Chlamydia felis*）和黴漿菌（*Mycoplasma*）結膜炎，以及未確診結膜炎的非特異性或症狀性治療。 * **劑型：** 市面上常見的眼藥膏配方會結合**多黏菌素B (Polymyxin B)**，以擴大其抗菌譜，涵蓋多種革蘭氏陰性菌（如綠膿桿菌）。
作用機制: Oxytetracycline is a bacteriostatic antibiotic that inhibits bacterial protein synthesis. * It reversibly binds to the **30S ribosomal subunit** of susceptible organisms. * This binding blocks the attachment of aminoacyl-tRNA to the mRNA-ribosome complex → **inhibits the addition of amino acids to the growing peptide chain** → halts bacterial growth and replication. * The addition of Polymyxin B (in commercial ointments) disrupts the bacterial cell membrane of gram-negative bacteria, altering permeability and causing cell death.
各物種劑量
- Chlamydial/Mycoplasma keratoconjunctivitis · Apply 4 times daily · topical ophthalmic · q6h · 3-4 weeks · Dramatic improvement should be noted in 3-4 days, but treatment should continue for 3-4 weeks for Chlamydia to break the reproductive cycle. Better treatment is oral doxycycline 25 mg PO twice daily for three weeks.
- Susceptible infections (when no other agent is suitable) · 10 mg/kg · IM/SC · q24h · Not specified · Only use in cats when no other agent is suitable.
- Susceptible infections · 10 mg/kg · IM/SC · q24h · Not specified
- Susceptible infections · 50 mg/kg loading dose, then 25 mg/kg · PO · q12h · up to 5 days · Give oral dose on an empty stomach.
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。
給藥途徑
禁忌症
- Known hypersensitivity to tetracyclines or polymyxin B
- Use of concentrated cattle/sheep depot formulations in small animals
- Pregnancy (last 2-3 weeks)
- Neonates (first month of life)
- Use in cats unless absolutely necessary
不良反應
- Local irritation
- Hypersensitivity reactions (rare)
- Potential for overgrowth of non-susceptible organisms (e.g., fungi) with prolonged use
- Vomiting
- Diarrhoea
- Depression
- Hepatotoxicity (rare)
- Fever
- Hypotension (following IV administration)
- Anorexia (especially in cats)
- Superinfections (with prolonged use)
- Renal tubular functional changes
- Teeth staining in developing animals
藥物相互作用
- Penicillins · Bactericidal action of penicillins may be inhibited by oxytetracycline · moderate
- Antacids (Mg, Ca, Al) · Binds tetracycline, significantly reducing its GI absorption · major
- Food or Milk products · Binds tetracycline, reducing its absorption · major
- Methoxyflurane · May increase the nephrotoxic effects · major
- Theophylline · GI effects of tetracyclines may be increased · moderate
監測
- Resolution of clinical signs (conjunctival hyperemia, chemosis, ocular discharge)
- Signs of local irritation or hypersensitivity
- Renal function (BUN, Creatinine, Urinalysis)
- Hydration status
- Gastrointestinal signs
過量
Topical overdose is highly unlikely to cause systemic toxicity. If severe local irritation occurs, flush the eye with sterile saline and discontinue use.
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。