阿奇黴素
**阿奇黴素 (Azithromycin)** 是一種廣效、半合成的巨環類（氮雜內酯類）抗生素。由於其極佳的藥代動力學特性，與紅黴素等較早期的巨環類藥物相比，給藥頻率較低，因此在獸醫學中被廣泛使用。 **主要臨床特徵：** * **卓越的組織穿透力：** 阿奇黴素會被吞噬細胞（巨噬細胞和多形核白血球）及纖維母細胞主動吸收，並遷移至感染部位。這使得組織中的藥物濃度可高達血清濃度的100倍。 * **長半衰期：** 該藥物具有非常長的組織半衰期（在狗體內可達90小時），允許在初始負荷劑量後採用脈衝式給藥（例如每3至5天給藥一次）。 * **抗菌譜：** 對多種革蘭氏陽性菌（如鏈球菌、葡萄球菌）、部分革蘭氏陰性菌（嗜血桿菌、博德氏桿菌）以及非典型病原體（包括肺炎黴漿菌、伯氏疏螺旋體、弓形蟲和巴爾通體）有效。 * **特定用途：** 常被用於治療犬博德氏桿菌肺炎、貓上呼吸道感染、貓巴爾通體症、犬吉氏巴貝斯蟲感染（與阿托伐醌併用），以及馬駒的馬紅球菌感染。 > **臨床要點：** 儘管用途廣泛，但阿奇黴素已被證實對清除貓的貓披衣菌 (Chlamydophila felis) 或貓血行黴漿菌 (Mycoplasma haemofelis) 無效。
作用機制: Azithromycin exerts its antibacterial effects by binding to the **50S ribosomal subunit** of susceptible microorganisms. * **Mechanism:** By binding to the 50S subunit, it blocks **transpeptidation** and **translocation** processes → inhibits RNA-dependent protein synthesis. * **Action Type:** It is generally considered **bacteriostatic**, but can be bactericidal at high concentrations or against highly susceptible organisms. * **Targeted Delivery:** The drug is actively transported to the site of infection by host phagocytic cells. During active phagocytosis, azithromycin is released locally, providing high concentrations directly at the site of bacterial invasion.
各物種劑量
- Susceptible infections · 5-10 mg/kg PO once daily for 3-5 days · PO · q24h · 3-5 days
- Susceptible infections (pulse dosing) · 5 mg/kg PO once daily for 2 days, then every 3-5 days for a total of 5 doses · PO · q24h then q3-5d · 5 doses total
- 'Derm' infections · 5-10 mg/kg PO once daily for 5-7 days. For animals that are difficult to pill, a dose given every 5 days (after the initial 5-7 day course of therapy) may be effective if continued treatment is necessary. · PO · q24h then q5d · 5-7 days initially
- Canine pyoderma · 10 mg/kg PO once daily for 5-10 days · PO · q24h · 5-10 days
- Babesia gibsoni (Asian genotype) infections · Atovaquone 13.3 mg/kg PO q8h with a fatty meal and Azithromycin 10 mg/kg PO once daily. Give both drugs for 10 days. · PO · q24h · 10 days · Reserve immunosuppressive therapy for cases that are not rapidly responding (3-5 days) to anti-protozoal therapy.
- Idiopathic lymphoplasmacytic (chronic) rhinitis · Doxycycline 3-5 mg/kg PO q12h, or azithromycin 5 mg/kg PO q24h in combination with piroxicam 0.3 mg/kg PO q24h. · PO · q24h · Long term · Used for immunomodulatory effects.
- Susceptible infections · 5-10 mg/kg · PO · q24h · May increase dosing interval to q48h after 3-5 days of treatment · Doses are empirical and subject to change
- Chlamydiosis (experimentally infected cockatiels) · Azithromycin 40 mg/kg PO once every other day (q48h) for 21 days · PO · q48h · 21 days · Birds were dosed via metallic feeding tube into crop using the commercially available human oral suspension.
給藥途徑
禁忌症
- Hypersensitivity to azithromycin or any other macrolide antibiotics
不良反應
- Vomiting (especially at high doses)
- Diarrhea
- GI cramping
- Potential hepatotoxicity
- Local tissue reactions (IV site)
- Muscle damage (IM injection)
- Diarrhea in foals
藥物相互作用
- Antacids (magnesium- and aluminum-containing) · May reduce the rate of absorption of azithromycin; separate dosages by 2 hours
- Cisapride · Other macrolides are contraindicated with cisapride due to potential for fatal arrhythmias; use with extreme caution or avoid
- Cyclosporine · Azithromycin may potentially increase cyclosporine blood levels; monitor carefully
- Digoxin · Other macrolides can increase digoxin levels; monitor carefully · major
- Pimozide · Contraindicated; acute deaths have occurred in humans
- Methylprednisolone · May increase serum levels of methylprednisolone · moderate
- Theophylline · May increase serum levels of theophylline · major
- Terfenadine · May increase serum levels of terfenadine · major
監測
- Clinical efficacy (resolution of infection signs)
- Adverse effects (especially GI distress or signs of hepatic impairment)
過量
Acute oral overdoses are unlikely to cause significant morbidity other than gastrointestinal distress, including **vomiting, diarrhea, and GI cramping**. Treatment should be supportive and symptomatic.
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