アジスロマイシン
**アジスロマイシン**は、アザライド・サブクラスに属する広域スペクトルの半合成マクロライド系抗生物質です。エリスロマイシンなどの古いマクロライド系と比較して投与頻度を減らすことができる非常に優れた薬物動態プロファイルを持つため、獣医療で広く使用されています。 **主な臨床的特徴:** * **優れた組織移行性:** アジスロマイシンは食細胞（マクロファージや多形核白血球）および線維芽細胞に能動的に取り込まれ、感染部位に移動します。これにより、組織内濃度は血清濃度の最大100倍に達することがあります。 * **長い半減期:** この薬は非常に長い組織半減期（犬で最大90時間）を示し、初期の負荷投与後にパルス投与（例：3〜5日ごと）を行うことが可能です。 * **抗菌スペクトル:** 様々なグラム陽性菌（レンサ球菌、ブドウ球菌など）、一部のグラム陰性菌（インフルエンザ菌、ボルデテラ属）、および非定型病原体（マイコプラズマ・ニューモニエ、ボレリア・ブルグドルフェリ、トキソプラズマ属、バルトネラ属など）に対して有効です。 * **特定の用途:** 犬のボルデテラ肺炎、猫の上部呼吸器感染症、猫のバルトネラ症、犬のバベシア・ギブソニ感染症（アトバコンとの併用）、および子馬のロドコッカス・エクイ感染症に頻繁に使用されます。 > **臨床上のポイント:** 幅広い用途があるにもかかわらず、アジスロマイシンは猫のクラミドフィラ・フェリス（Chlamydophila felis）やマイコプラズマ・ヘモフェリス（Mycoplasma haemofelis）の排除には無効であることが示されています。
作用機序: 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.
動物種別の用量
- 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.
投与経路
禁忌
- Hypersensitivity to azithromycin or any other macrolide antibiotics
有害事象
- Vomiting (especially at high doses)
- Diarrhea
- GI cramping
- Potential hepatotoxicity
- Local tissue reactions (IV site)
- Muscle damage (IM injection)
- Diarrhea in foals
薬物相互作用
- 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
モニタリング
- Clinical efficacy (resolution of infection signs)
- Adverse effects (especially GI distress or signs of hepatic impairment)
過量投与
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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