Dactinomycin is a potent cytotoxic antibiotic derived from *Streptomyces parvullus*. It is a cornerstone chemotherapeutic agent primarily used in the treatment of specific pediatric solid tumors and gestational trophoblastic neoplasia. It functions as a DNA intercalator, disrupting transcription and leading to cell death, particularly in rapidly dividing cells. Due to its high toxicity profile, it is classified as a hazardous drug requiring specialized handling and administration.
Adult: Gestational Trophoblastic Neoplasia: 12 mcg/kg IV daily for 5 days as a single agent, repeated every 2-3 weeks. Testicular Cancer: Part of combination regimens (e.g., PEB), typically 1000 mcg/m² on Day 1, repeated every 3 weeks. DOSE IS HIGHLY PROTOCOL-SPECIFIC.
Note: FOR INTRAVENOUS USE ONLY. Reconstitute 0.5mg vial with 1.1 mL of sterile water for injection (without preservative) to yield 0.5 mg/mL. Further dilute in 20-50 mL of 5% Dextrose or Normal Saline. Administer via slow IV push over 2-5 minutes or a short IV infusion (10-20 mins) through a free-flowing IV line or central venous catheter. Observe for extravasation continuously. Flush line before and after administration.
Dactinomycin intercalates into the minor groove of DNA, preferentially at GpC sequences, forming a stable complex. This binding physically impedes the progression of RNA polymerase, thereby inhibiting DNA-directed RNA synthesis (transcription). It also causes single-strand DNA breaks, likely through free radical generation or topoisomerase II inhibition. The net effect is a blockade in the production of essential proteins and enzymes, leading to cell cycle arrest (primarily in G1 phase) and apoptosis.
Pregnancy: FDA Pregnancy Category D (Positive evidence of human fetal risk). Can cause fetal harm, including teratogenicity and death. Contraindicated, especially in first trimester. Effective contraception required during and after treatment.
Driving: May cause fatigue, malaise, or dizziness. Patients should be cautioned against driving or operating machinery if affected.
| Live Vaccines (e.g., MMR, Varicella) | Risk of disseminated vaccine-induced infection due to immunosuppression. | Contraindicated |
| Other Myelosuppressive Agents (e.g., Cyclophosphamide, Doxorubicin) | Additive bone marrow toxicity; requires careful monitoring and dose adjustments. | Major |
| Radiation Therapy | Enhanced radiation effects on tumor and normal tissues (radiosensitization). Recall of skin/mucosal toxicity in previously irradiated areas. | Major |
| Phenytoin | Dactinomycin may decrease phenytoin absorption, reducing its anticonvulsant efficacy. | Moderate |
| Vitamin K Antagonists (Warfarin) | Potential increased anticoagulant effect due to decreased synthesis of clotting factors and possible thrombocytopenia. | Moderate |
Same composition (Dactinomycin (0.5mg)), different brands: