Idarubicin — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	IV	1-2 mg/m²	q24h for 3 days, or q21d as a single dose	Duration: Cycles depending on protocol Notes: Administer as a slow IV infusion over 10-15 minutes; monitor for extravasation.
Cat	IV	0.5-1 mg/m²	q24h for 3 days, or q21d	Duration: Cycles depending on protocol Notes: Use with caution; cats are sensitive to anthracyclines.
Horse	IV	Not established	Not established	Duration: Not established Notes: Limited data; use only with extreme caution and under specialist guidance.

Clinical Indications & Species Uses

General Indications

Treatment of various neoplastic conditions, especially leukemias and lymphomas

Dog (Canine)

Acute myeloid leukemia (AML)
Lymphoma (as part of combination protocols)
Myelodysplastic syndromes

Cat (Feline)

Lymphoma (rescue therapy)
Acute leukemia

Pharmacology & Mechanism of Action

Drug Class: Anthracycline Antibiotic | Pharmacological Group: Antineoplastic Agent

Mechanism of Action: Idarubicin is an anthracycline antibiotic that intercalates between DNA base pairs, inhibiting topoisomerase II and preventing DNA replication and transcription. It also generates free radicals that cause DNA strand breaks and lipid peroxidation, leading to cell death. Its active metabolite, idarubicinol, contributes to the cytotoxic effect.

Pharmacodynamics: Idarubicin is a potent cytotoxic agent with a broad spectrum of activity against various tumors. It is more lipophilic than daunorubicin, leading to enhanced cellular uptake and increased potency. It exhibits cell cycle non-specific activity, affecting both dividing and resting cells. Its cardiotoxic potential is lower than that of doxorubicin but still significant.

⚡ Pharmacokinetics Summary

Absorption: Oral absorption is variable and incomplete; bioavailability is approximately 30% in humans. In veterinary patients, oral absorption is also erratic, so IV administration is preferred for reliable dosing.

Distribution: Widely distributed into tissues, with high concentrations in the liver, lungs, kidneys, and spleen. It crosses the blood-brain barrier poorly. Protein binding is approximately 97% in humans.

Metabolism: Extensively metabolized in the liver to idarubicinol, which is pharmacologically active and has a longer half-life than the parent drug.

Excretion: Primarily excreted via bile into feces; renal excretion accounts for about 5-10% of the dose. In animals with hepatic impairment, clearance is reduced.

Half-Life: In dogs, the terminal half-life of idarubicin is approximately 15-20 hours; idarubicinol has a half-life of 40-60 hours. In cats, half-life may be longer.

Bioavailability: Oral bioavailability is low and variable (approximately 30% in humans); IV administration ensures complete bioavailability.

Protein Binding: Approximately 97% protein-bound in humans; similar in animals.

Available Formulations & Strengths

Injectable Solution 1 mg/mL, 5 mg/mL (IV)

Oral Capsule 5 mg, 10 mg (PO)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to idarubicin or other anthracyclines
Severe hepatic impairment
Severe renal impairment
Pre-existing cardiomyopathy or significant cardiac disease
Severe myelosuppression
Pregnancy and lactation (teratogenic and embryotoxic)

Warnings & Clinical Precautions:

Extremely vesicant; avoid extravasation during IV administration
May cause severe myelosuppression; monitor CBC closely
Cardiotoxic; cumulative dose should be limited (e.g., <180 mg/m² in dogs)
Hepatotoxic and nephrotoxic; monitor liver and kidney function
Immunosuppressive; use with caution in patients with active infections
Use protective equipment when handling; avoid skin contact
Not for use in food animals due to lack of withdrawal data

Adverse Effects & Reactions

Common:

Myelosuppression (neutropenia, thrombocytopenia, anemia)
Gastrointestinal signs (vomiting, diarrhea, anorexia)
Alopecia
Lethargy

Serious / Severe:

Cardiotoxicity (arrhythmias, congestive heart failure)
Extravasation injury (tissue necrosis)
Secondary leukemia
Severe infection due to neutropenia

Rare:

Hepatotoxicity
Nephrotoxicity
Anaphylaxis
Tumor lysis syndrome

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other cardiotoxic drugs (e.g., doxorubicin, cyclophosphamide)	Increased risk of cardiotoxicity	High
Myelosuppressive agents (e.g., vincristine, methotrexate)	Additive bone marrow suppression	High
Hepatotoxic drugs (e.g., azathioprine, ketoconazole)	Increased risk of hepatotoxicity	Moderate
Live vaccines	Reduced efficacy and increased risk of infection	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

Severe myelosuppression
Cardiac arrhythmias
Gastrointestinal ulceration
Hepatotoxicity
Renal failure

Emergency Treatment Protocol: There is no specific antidote. Treatment is supportive: hospitalization, IV fluids, antiemetics, antibiotics for infections, blood transfusions if needed, and cardiac monitoring. Consider granulocyte colony-stimulating factor (G-CSF) for neutropenia. In cases of recent overdose, consider activated charcoal if oral ingestion, but IV overdose requires immediate supportive care.

Food Animal Withdrawal Times

Not approved for use in food animals; no withdrawal times established. Use in food animals is prohibited.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F); protect from light.

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Store in original carton until use. Reconstituted solutions should be used within 24 hours if refrigerated.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; used extra-label in veterinary oncology.

Extra-Label (Off-Label) Use: In the US, extra-label use in food animals is prohibited. In companion animals, extra-label use is permitted under AMDUCA with appropriate veterinary oversight.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Idarubicin is a potent anthracycline used primarily in veterinary oncology for the treatment of leukemias and lymphomas, especially in dogs and cats. It is often used as a rescue agent when resistance to doxorubicin develops. Due to its vesicant nature, IV administration must be done carefully via a central line or a well-placed peripheral catheter. Close monitoring of complete blood counts and cardiac function is essential. The drug is contraindicated in animals with significant cardiac or hepatic disease. Because of its potential for severe toxicity, it should only be used by veterinarians experienced in chemotherapy. In food animals, its use is strictly prohibited due to lack of withdrawal data and potential for residues.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)