Dactinomycin
Actinomycin D
Also known as: Cosmegen · Lyovac · Actinomycin D · DTIC · actinomycin C(1) · meractinomycin · NSC-3053 · Ac-De · Bioact-D · Dacmozen
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
This dose is based on body surface area (mg/m²). Convert body weight to body surface area before dosing.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| 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 | 🌎 NA |
| Lymphoma (rescue protocols), sarcomas, and carcinomas | 0.5-0.75 mg/m2 | IV | q2-3wk | Administer slowly over 20 min | 🌍 EU |
- Antineoplastic protocols (e.g., rescue therapy for lymphomas, sarcomas): Dose is based on body surface area (m2). Consultation with a veterinary oncologist is strongly recommended.
- Lymphoma (rescue protocols), sarcomas, and carcinomas: Must be administered via a preplaced catheter due to vesicant properties.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
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.
Mechanism of action
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.
Safety & warnings
Contraindications
- Hypersensitivity to dactinomycin
- Pregnancy (teratogenic and embryotoxic)
Adverse effects
- 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
Precautions
WARNING: Severe Vesicant and Highly Toxic
- Extravasation Risk: Can cause extensive pain and tissue damage. Must be administered via a perfectly placed IV catheter, ideally using a 'two-needle' technique and slow infusion into a running IV line.
- MDR1 Mutation: Use with extreme caution or avoid in breeds susceptible to the MDR1-allele mutation (Collies, Australian Shepherds, Shelties, Long-haired Whippets) due to high risk of fatal toxicity.
- Organ Dysfunction: Use with caution in patients with preexisting bone marrow depression, hepatic dysfunction, or active infections.
- Hazardous Drug: Chronic exposure increases mutagenic, teratogenic, and carcinogenic risks for healthcare workers. Strict hazardous drug handling, preparation, and disposal protocols are required.
- Pregnancy/Nursing: Embryotoxic and teratogenic (FDA Category C). Avoid use in pregnant or nursing animals.
Drug interactions
Additive cardiotoxicity may occur if used concurrently or sequentially.
May cause additive myelosuppression.
Patients may require higher dosages of vitamin K when receiving dactinomycin.
Monitoring
- 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
Pharmacokinetics
Absorption
Poorly absorbed from the GI tract; must be administered intravenously.
Distribution
Rapidly distributed into tissues. High concentrations are found in bone marrow and nucleated cells. It crosses the placenta.
Metabolism
Undergoes minimal hepatic metabolism.
Elimination
The majority of the drug is excreted unchanged in the bile and urine.
Overdose
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).
Available products
Formulations
- Powder for injection (lyophilized)
Human-labeled
- Dactinomycin Powder for Injection, lyophilized: 500 micrograms with mannitol 20 mg in vials; Cosmegen® (Merck); (Rx)
Regulatory status
POM (Prescription Only Medicine). Handled under strict cytotoxic safety regulations.
POM (Prescription Only Medicine).
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store the commercially available powder at room temperature and protect from light. Reconstitution: Must use sterile water for injection without preservatives, as preservatives will cause precipitation. Use the solution immediately after reconstitution and discard any unused portion. If stored in the refrigerator, it loses 2-3% potency over 6 hours. Note: IV fluid sterilizing filters (cellulose ester membrane) may partially remove the drug.
Client information
Dactinomycin is a potent chemotherapy drug used to treat certain cancers. Because it is very strong, it requires careful monitoring.
- Toxicity Signs: Contact your veterinarian immediately if your pet shows signs of serious illness, including bloody vomiting or diarrhea, abnormal bleeding or bruising, straining to urinate, severe lethargy/depression, signs of infection (fever), or shortness of breath.
- Oral Sores: Check your pet's mouth periodically for sores or ulcers, which can make eating painful.
- Safety at Home: Because this drug is eliminated in your pet's waste and has the potential to cause cell damage, wear gloves when handling your pet's urine, feces, or vomit for a few days after treatment. Wash your hands thoroughly afterward.
- Breeding/Pregnancy: This drug can cause birth defects. Do not breed pets receiving this medication.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.