Doxorubicin(Doxorubicin) - Uses, Dosage and Side Effects

Doxorubicin for dogs and cats is an anthracycline chemotherapy agent used in veterinary oncology to treat a range of malignant cancers. In India, lymphoma, osteosarcoma, soft tissue sarcoma, and mammary carcinoma are among the cancers most frequently treated with doxorubicin in dogs.

Doxorubicin is often used as part of a multi-drug chemotherapy protocol designed to achieve the broadest possible tumour cell kill.

Doxorubicin damages the DNA of cancer cells and interferes with the processes they need to reproduce, causing susceptible cancer cells to stop growing and die.

Cancer cells tend to divide more rapidly than many normal cells, which makes them particularly vulnerable to medicines that interfere with cell division.

Doxorubicin can also produce harmful free radicals that contribute to its anticancer effect but can damage certain normal tissues, particularly the heart. This is one reason why cumulative dosing and cardiac monitoring are important in dogs.

Doxorubicin works in cats by damaging cancer-cell DNA and interfering with cancer-cell growth and division.

It may be used for selected cancers in cats, but the treatment plan is tailored to the individual patient because cats have a particular risk of kidney toxicity with cumulative doxorubicin exposure.

Before treatment, an expert feline vet may evaluate kidney function and other health parameters to determine whether doxorubicin is appropriate and whether the treatment schedule needs modification.

Doxorubicin dosage for dogs is calculated based on body surface area (BSA) rather than body weight, as this more accurately accounts for metabolic differences between patients of varying sizes. Infuse slowly over 15 to 30 minutes to reduce the risk of anaphylactoid reactions. Clinicians routinely administer premedication with antihistamines before each infusion.

Protocols vary by cancer type. In lymphoma, doxorubicin is administered every 3 weeks as part of the CHOP protocol. In osteosarcoma, it is typically given every 2 to 3 weeks for 4 to 6 cycles following amputation. Complete blood counts are checked before each dose to confirm the patient is fit to receive treatment. Dogs with pre-existing cardiac disease require echocardiographic assessment before starting doxorubicin, as cumulative cardiac toxicity is a recognised risk with repeated dosing.

Doxorubicin dosage for cats is also BSA-based and administered by slow intravenous infusion. Cats generally receive lower doses per cycle than dogs because they are more sensitive to gastrointestinal and renal toxicity. Infusion duration may be extended in cats to minimise the risk of acute reaction. Blood count monitoring before each infusion is mandatory. Cats with pre-existing renal disease require careful nephrotoxicity monitoring throughout the treatment course, as doxorubicin can contribute to cumulative renal damage in this species.

Doxorubicin carries significant toxicity potential. Close monitoring throughout each treatment cycle is essential.

Cats may experience severe gastrointestinal signs, bone marrow suppression, renal toxicity, and anaphylactoid reactions during infusion. Cats are more sensitive to doxorubicin-induced nephrotoxicity than dogs. Assess renal function before each infusion using blood urea nitrogen, creatinine levels, SDMA, and urinalysis. Extravasation causes severe and potentially permanent tissue damage in cats and requires immediate emergency management by a trusted 24/7 pet vet.

Doxorubicin overdose in dogs causes severe bone marrow failure, profound gastrointestinal toxicity, acute cardiac arrhythmias, and potentially fatal sepsis from neutropenia. Because it is administered in a controlled clinical setting, dosing errors are uncommon but life-threatening when they occur. Immediate intensive supportive care, including intravenous fluids, haematopoietic growth factors, and broad-spectrum antibiotics, is required. Contact your veterinary oncologist immediately if overdose is suspected.

Cats are more susceptible to doxorubicin overdose effects, particularly acute renal failure, severe gastrointestinal toxicity, and cardiovascular collapse. Any suspected overdose in a cat requires immediate emergency hospitalisation. Because there is no specific antidote, rapid initiation of supportive care is the critical determinant of outcome. Do not delay seeking emergency veterinary attention.

Doxorubicin is a cytotoxic drug classified as a vesicant, meaning it causes severe tissue destruction on contact outside a blood vessel. Urine, faeces, and vomit from treated pets contain the drug for approximately 48 to 72 hours after infusion. Wear disposable gloves when handling bodily waste during this period and dispose of it hygienically. Wash hands thoroughly after contact with the treated patient.

Monitor your pet closely for signs of neutropenia between day 7 and day 14 post-infusion, including fever, lethargy, and loss of appetite. These signs may indicate sepsis, which is a life-threatening complication requiring emergency hospitalisation. Attend all scheduled blood monitoring appointments, as dose adjustments depend on haematological findings from each cycle.

Contact your veterinary oncologist immediately if your pet develops fever above 39.5°C, collapse, severe lethargy, complete appetite loss, uncontrolled vomiting or diarrhoea, or significant weakness within 7 to 14 days of a doxorubicin infusion. Also report any swelling, pain, skin discolouration, or tissue changes at the injection site, as these may indicate extravasation injury requiring urgent wound management to prevent progressive tissue destruction.

Doxorubicin for dogs and cats is a cornerstone chemotherapy agent in veterinary oncology, offering meaningful tumour control and survival extension in several malignancies when used under specialist supervision. Working closely with your veterinary oncologist and promptly reporting any changes in your pet's condition are essential throughout treatment.