アシクロビル
**アシクロビル (Acyclovir)** は合成プリンヌクレオシド類似体であり、獣医学においては主に特定のヘルペスウイルスに対する抗ウイルス作用を目的として使用されます。 主な臨床応用： * **鳥類医学**：**パチェコ病**（鳥類において非常に致死率の高いヘルペスウイルス感染症）の治療および予防。 * **猫科医学**：**猫ヘルペスウイルス1型 (FHV-1)** 感染症、特に角膜や結膜の病変の管理。*臨床のポイント：ファムシクロビル、ガンシクロビル、シドフォビルなどの新しい抗ウイルス薬と比較してFHV-1に対する活性は比較的弱く、猫では全身性毒性のリスクが高くなります。* * **馬科医学**：**馬ヘルペスウイルス1型 (EHV-1)** 脊髄脳症の治療として研究されていますが、馬における経口バイオアベイラビリティが極めて低い（<4%）ため、治療効果を得るのが困難です。 ヒトでは非常に有効ですが、獣医学領域での使用は、薬物動態のばらつき、特定の動物種（馬など）での経口吸収の悪さ、および潜在的な毒性（猫における腎毒性や骨髄抑制など）によって制限されることがよくあります。
作用機序: Acyclovir is a prodrug that requires activation by viral enzymes, making it highly specific to infected cells. 1. **Viral Entry**: Acyclovir enters the virus-infected cell. 2. **Initial Phosphorylation**: It is preferentially phosphorylated by **viral thymidine kinase** into acyclovir monophosphate. 3. **Subsequent Phosphorylation**: Host cell kinases further convert it into the active form, **acyclovir triphosphate**. 4. **DNA Chain Termination**: Acyclovir triphosphate acts as a competitive inhibitor of **viral DNA polymerase**. It incorporates into the growing viral DNA chain → lacks the 3'-hydroxyl group needed for further elongation → causes **premature DNA chain termination** and halts viral replication.
動物種別の用量
- Herpesvirus-1 infections · 10-25 mg/kg PO twice daily · PO · q12h · Never begin therapy until diagnostic evaluation is completed. May be toxic in cats; monitor CBC every 2-3 weeks.
- EHV-1 outbreaks (prevention or treatment) · 10 mg/kg PO 5 times daily or 20 mg/kg PO q8h · PO · 5 times daily or q8h · Although efficacy is undetermined, anecdotal use may have had some efficacy. However, the drug's very low oral bioavailability suggests that oral dosing is unlikely to be of much benefit.
- Treatment of Pacheco's Disease · 80 mg/kg PO q8h or 40 mg/kg q8h IM · PO/IM · q8h · Maximum 72 hours for IM · Do not use parenterally for more than 72 hours as it can cause tissue necrosis at site of injection.
- Treatment of Pacheco's Disease · 80 mg/kg in oral suspension once daily PO; mix suspension with peanut butter or add to drinking water 50 mg in 4 oz of water · PO · q24h · 7-14 days
- Individual treatment · 80 mg/kg PO or IM twice daily · PO/IM · q12h
- Prophylaxis (Exposed birds) · 25 mg/kg IM once, then acyclovir is added to drinking water at 1 mg/mL and to the food at 400 mg/quart of seed · IM, then PO · Once IM, then continuous PO · Minimum of 7 days · Give IM with caution as it is very irritating.
- Prophylaxis (Quaker parrots) · 80 mg/kg q8h · PO (gavage) · q8h · 7 days
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Dehydrated states
- Pre-existing renal function impairment
- Hypersensitivity to acyclovir or related antivirals
- Pre-existing neurologic deficits
- Previous neurologic reactions to other cytotoxic drugs
有害事象
- Thrombophlebitis (with parenteral use)
- Acute renal failure
- Encephalopathologic changes (rare)
- Gastrointestinal disturbances (vomiting, diarrhea)
- Leukopenia (cats)
- Anemia (cats)
- Tissue necrosis (if given IM for >72 hours in birds)
薬物相互作用
- Nephrotoxic medications (e.g., Amphotericin B, Aminoglycosides) · Concomitant administration with IV acyclovir may increase the potential for nephrotoxicity. Amphotericin B may potentiate antiviral effects but significantly increases nephrotoxic risk.
- Zidovudine · Concomitant use may cause additional CNS depression.
モニタリング
- Renal function tests (BUN, Serum Creatinine) with prolonged or IV therapy
- Complete Blood Count (CBC) every 2-3 weeks in cats to monitor for leukopenia and anemia
- Hydration status
過量投与
Acute oral overdosage is unlikely to cause significant toxicity. * **Clinical Signs**: Gastrointestinal signs (vomiting, diarrhea, lethargy) predominate. Renal failure is possible with higher doses due to drug crystallization in the renal tubules. Crystalluria and elevated renal values occurred at 188.7 mg/kg in a dog. * **Treatment**: Consider gastrointestinal decontamination at doses of **150 mg/kg or higher**. Below 150 mg/kg, manage symptomatically as GI signs will likely predominate. Ensure adequate hydration to maintain urine flow and prevent crystalluria.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。