Dactinomycin
Dactinomycin (also known as Actinomycin D) is a parenteral antitumor antibiotic isolated from *Streptomyces parvullus*. It is utilized in veterinary oncology primarily for the adjunctive treatment of lymphoreticular neoplasms, bone and soft tissue sarcomas, and carcinomas in small animals, as well as a rescue therapy for canine lymphomas. **Clinical Pearls & Key Characteristics:** * **Vesicant:** Dactinomycin is a severe vesicant. Extravasation can cause devastating tissue necrosis and sloughing. Strict intravenous administration via a perfectly placed, clean IV catheter is mandatory. * **MDR1 Substrate:** It is actively transported by the P-glycoprotein (P-gp) pump. Breeds with the ABCB1 (MDR1) mutation (e.g., Collies, Australian Shepherds) are at a significantly increased risk for severe, life-threatening toxicity. Testing is highly recommended prior to use. * **Toxicity Profile:** Characterized by significant myelosuppression and gastrointestinal toxicity, which can be life-threatening.
กลไกการออกฤทธิ์: 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.
ขนาดยาตามชนิดสัตว์
- 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.
ขนาดยาเป็นข้อมูลอ้างอิงทางคลินิกสำหรับสัตวแพทย์ผู้มีใบอนุญาต โปรดตรวจสอบกับฉลากล่าสุดและผู้ป่วยแต่ละรายเสมอ
วิธีการให้ยา
ข้อห้ามใช้
- Hypersensitivity to dactinomycin
- Pregnancy (teratogenic and embryotoxic)
อาการไม่พึงประสงค์
- 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
อันตรกิริยาระหว่างยา
- 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.
การติดตาม
- 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
การได้รับยาเกินขนาด
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).
ข้อมูลอ้างอิงยาของ VetSheet มีไว้สำหรับสัตวแพทย์ผู้มีใบอนุญาตเพื่อช่วยในการตัดสินใจทางคลินิก ไม่ใช่สิ่งทดแทนการวินิจฉัยของผู้เชี่ยวชาญหรือฉลากล่าสุดของผู้ผลิต