齊多夫定
齊多夫定 (Zidovudine, AZT) 是一種**核苷酸反轉錄酶抑制劑 (NRTI)**，在獸醫學中主要作為貓免疫缺陷病毒 (FIV) 或貓白血病病毒 (FeLV) 的輔助治療。 * **臨床應用**：雖然它能降低受感染貓咪的病毒載量並改善臨床症狀（如口炎或神經系統症狀），但它無法治癒疾病，也可能無法大幅改變疾病的長期自然病程。 * **臨床要點**：由於反轉錄病毒會整合到宿主基因組中，像齊多夫定這類的 NRTI 主要作用是防止新細胞被感染，而非清除已感染的細胞。
作用機制: Zidovudine is a synthetic thymidine analogue. * **Mechanism**: It is converted *in vivo* by cellular kinases into its active metabolite, **zidovudine triphosphate**. * **Pathway**: Zidovudine triphosphate competes with natural thymidine triphosphate for incorporation into viral DNA by **viral RNA-directed DNA polymerase** (→ **reverse transcriptase**). * **Effect**: Because zidovudine lacks a 3'-OH group, its incorporation prevents the formation of phosphodiester linkages, leading to **DNA chain termination** and a virustatic effect against retroviruses. * It also possesses some activity against gram-negative bacteria and can exhibit host cell cytotoxicity (particularly in rapidly dividing cells like bone marrow).
各物種劑量
- Adjunctive therapy of FeLV and FIV · 5-10 mg/kg PO or SC q12h · PO, SC · q12h · Higher dose should be used carefully as side effects can develop. For SC injection, dilute lyophilized product in isotonic sodium chloride to prevent local irritation. For PO, syrup or gelatin capsules can be used.
- Adjunctive therapy of FeLV and FIV · 5-10 mg PO or SC q12h · PO, SC · q12h · Note: Dose is in mg per cat, not mg/kg. Higher dose should be carefully used in FeLV-infected cats because side effects, particularly non-regenerative anemia, can develop.
- FeLV · 5 mg/kg PO or SC q12h · PO, SC · q12h · If giving SC, dilute in sterile normal saline to prevent local irritation. Check CBC weekly the first month.
- FIV encephalopathy · 20 mg/kg PO q12h · PO · q12h
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
- Patients with a history of life-threatening hypersensitivity reactions to zidovudine
不良反應
- Non-regenerative anemia (most common in cats, dose-dependent)
- Reductions in RBCs, PCV, and hemoglobin
- Diarrhea
- Weakness
- Granulocytopenia (reported in humans)
- Gastrointestinal effects
藥物相互作用
- Azole Antifungals (e.g., ketoconazole) · May increase zidovudine levels
- Atovaquone · May increase zidovudine levels
- Doxorubicin · May antagonize each other's effects; avoid concurrent use. Also increases risk of hematologic toxicity.
- Interferon alfa · Increased risk for hematologic and hepatotoxicity
- Probenecid · May increase zidovudine levels
- Myelo-/Cytotoxic Drugs (e.g., chloramphenicol, flucytosine, vincristine, vinblastine) · Administered with zidovudine may increase the risk of hematologic toxicity
- Rifampin · May decrease blood levels (AUC) of zidovudine
監測
- CBC (Complete Blood Count): Weekly for the first month of treatment (non-regenerative anemia is common, especially at higher doses). If stable, monthly checks are sufficient.
- Hematocrit: If PCV drops below 20%, treatment should be discontinued (anemia usually resolves within a few days).
- CD4/CD8 ratios (if possible)
- Clinical efficacy and improvement of signs
過量
Human adults and children have survived massive oral overdoses (up to 50 grams) without permanent sequelae. * **Clinical Signs**: Vomiting and transient hematologic effects (e.g., bone marrow suppression) are the most consistent adverse effects reported with acute overdoses. * **Management**: Treatment is largely supportive and symptomatic, focusing on gastrointestinal decontamination if caught early, and monitoring hematologic parameters.
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。