Oxytetracycline (Ophthalmic)

**Oxytetracycline** is a broad-spectrum bacteriostatic antibiotic belonging to the tetracycline class. * **Veterinary Use:** In veterinary ophthalmology, it is most frequently utilized in cats for the treatment of *Chlamydia felis* and *Mycoplasma* conjunctivitis, as well as for nonspecific or symptomatic therapy of undiagnosed conjunctivitis. * **Formulation:** It is commercially available as an ophthalmic ointment in combination with **Polymyxin B**, which extends its spectrum to include many gram-negative organisms (such as *Pseudomonas*). > **Clinical Pearl:** While topical oxytetracycline is effective for managing clinical signs of chlamydial conjunctivitis, it often fails to clear the systemic carrier state. Systemic therapy (e.g., oral doxycycline) is generally preferred for complete clearance of the organism.

กลไกการออกฤทธิ์: 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.

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