放線菌素D (Dactinomycin)
Dactinomycin（又稱 Actinomycin D）是一種從微小鏈黴菌 (Streptomyces parvullus) 中提取的注射用抗腫瘤抗生素。在獸醫腫瘤學中，主要用於小動物淋巴網狀內皮腫瘤、骨與軟組織肉瘤及癌的輔助治療，也是犬淋巴瘤救援療法的用藥之一。 **臨床要點與特徵：** * **發泡劑 (Vesicant)：** 具有強烈刺激性，若藥物外滲會導致嚴重的組織壞死與脫落，必須確保靜脈導管留置完美。 * **MDR1 基因突變：** 該藥物由 P-醣蛋白 (P-gp) 幫浦主動運輸。帶有 ABCB1 (MDR1) 基因突變的犬種（如牧羊犬、澳洲牧羊犬）具有極高的致命毒性風險，強烈建議用藥前進行基因檢測。 * **毒性特徵：** 具有顯著的骨髓抑制與胃腸道毒性，可能危及生命。
作用機制: Dactinomycin is a cell-cycle phase-nonspecific antineoplastic agent. * **Intercalation:** The drug intercalates into the minor groove of the DNA double helix, specifically between adjacent guanine-cytosine base pairs. * **Transcription Inhibition:** This stable dactinomycin-DNA complex physically blocks the progression of **DNA-dependent RNA polymerase** → inhibits transcription of messenger RNA (mRNA) → disrupts protein synthesis and leads to cell death. * It also possesses some immunosuppressive and hypocalcemic properties.
各物種劑量
- Antineoplastic protocols (e.g., rescue therapy for lymphomas, sarcomas) · 0.5-1 mg/m 2 (NOT mg/kg) · IV · over 20 minutes; repeated at 1-3 week intervals · Depending on the protocol · Dose is based on body surface area (m2). Consultation with a veterinary oncologist is strongly recommended.
- Lymphoma (rescue protocols), sarcomas, and carcinomas · 0.5-0.75 mg/m2 · IV · q2-3wk · Administer slowly over 20 min · Must be administered via a preplaced catheter due to vesicant properties.
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
- Hypersensitivity to dactinomycin
- Pregnancy (teratogenic and embryotoxic)
不良反應
- Bone marrow depression (anemia, leukopenia, thrombocytopenia)
- Gastrointestinal toxicity (diarrhea, ulcerative stomatitis, GI ulceration)
- Severe tissue damage and pain (if extravasated)
- Hyperuricemia (may require allopurinol)
- Hepatotoxicity
藥物相互作用
- Doxorubicin · Additive cardiotoxicity may occur if used concurrently or sequentially. · major
- Myelosuppressive drugs (e.g., chloramphenicol, flucytosine, colchicine, other antineoplastics) · May cause additive myelosuppression.
- Vitamin K · Patients may require higher dosages of vitamin K when receiving dactinomycin.
監測
- Efficacy (tumor measurement/response)
- Complete Blood Count (CBC) with differential and platelets (prior to each dose and at nadir)
- Hepatic function tests
- Oral cavity examinations (check for ulcerative stomatitis)
- IV catheter site for any signs of extravasation during administration
過量
Due to the extreme toxic potential of this agent, iatrogenic overdoses must be strictly avoided. Double-check all dosage calculations (ensure dosing is in **mg/m2**, not mg/kg). Overdose will result in severe, potentially fatal bone marrow suppression and gastrointestinal ulceration. Treatment is entirely symptomatic and supportive (e.g., broad-spectrum antibiotics, blood transfusions, aggressive fluid therapy, GI protectants).
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。