Vetdrugs 2.0Dacarbazine, also known as DTIC, is a triazene antineoplastic prodrug used in selected veterinary chemotherapy protocols. Its principal applications are rescue treatment of relapsed lymphoma and treatment of selected melanomas and soft-tissue sarcomas in dogs. It is more often used after other agents or within combination regimens than as a primary single agent.
Group
Antineoplastic alkylating agent
Mechanism of Action
Hepatic cytochrome P450 metabolism converts dacarbazine to active intermediates, including MTIC, that generate DNA-methylating species. Methylation of DNA bases, especially guanine, disrupts normal DNA processing and activates damage responses that can lead to tumor-cell death. It acts as a monofunctional alkylating agent and is generally considered cell-cycle nonspecific. Metabolic activation contributes to variation in drug response.
Dose Rates
Dog
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Chemotherapy | Reference only | IV | Body-surface-area protocols: 200 mg/m² daily for 5 days, repeated every 3 weeks; alternatively 800–1000 mg/m² every 3 weeks. These are distinct protocols and require BSA calculation. | |
| Alternative chemotherapy infusion | Reference only | IV | 800–1000 mg/m² infused over 5–8 hours, repeated every 2–3 weeks. Body-surface-area protocol; not mg/kg. |
Indications
- Rescue chemotherapy for relapsed or refractory lymphoma in dogs, including selected combination protocols with doxorubicin.
- Treatment of selected canine malignant melanomas within specialist oncology protocols, with variable clinical response.
- Treatment of selected canine soft-tissue sarcomas when included in an individualized rescue or combination chemotherapy plan.
Contraindications
- Cats
- Food-producing animals
- Hypersensitivity to dacarbazine
- Use cautiously with pre-existing marrow suppression, hepatic or renal dysfunction, or active infection.
Interactions
- Other marrow-suppressing medicines can increase hematologic toxicity.
- Rifampin, phenobarbital and phenytoin may increase metabolism; the clinical effect requires assessment.
Adverse effects
- Leukopenia
- Nausea, vomiting and diarrhea
- Thrombocytopenia and delayed marrow toxicity
- Extravasation injury, venous spasm and phlebitis
- Rare severe hepatic injury, renal impairment and photosensitivity
Toxicity
Myelosuppression and gastrointestinal injury limit dosing.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| DTIC 200 mg vial | Injection | 200 mg / vial | IV |
Monitoring and Administration
Monitor CBC before treatment and during marrow recovery.
Protect the vial from light. Dilute the prescribed dose in 50–100 mL of 0.9% saline; use a defined oncology protocol.
Include differential leukocyte and platelet counts, renal and hepatic testing during treatment; marrow nadirs can be delayed for weeks.
Use cytotoxic-drug handling precautions during preparation, administration and waste disposal. Avoid extravasation; concentrated injection can be painful.
Reconstitution stability depends on the exact presentation. The additional source describes up to 72 hours refrigerated or 8 hours at room temperature after sterile-water reconstitution; further diluted saline/D5W solution up to 24 hours refrigerated or 8 hours at room temperature. Confirm the actual vial instructions before applying these periods.