Cyclophosphamide
Also known as: Cytoxan, Neosar, Procytox, Endoxan, Endoxana
> **Important Safety Warning**: This is a potent chemotherapy drug. Follow all handling instructions carefully. * **Handling**: Do not break or crush tablets. Wash hands thoroughly after handling. Avoid direct contact with your pet's urine, feces, or vomit while they are on this medication. * **Urination**: Take your dog for frequent walks to encourage urination, especially in the morning. This helps prevent bladder irritation. * **When to call the vet**: Contact your veterinarian immediately if you notice blood in the urine, straining to urinate, abnormal bleeding, bruising, severe lethargy, vomiting, or diarrhea.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Immunosuppressant (ITP or IMHA)
- To slow progression of FIP
- Chemical shearing agent
- Neoplastic diseases
- Antineoplastic (lymphoma) in rabbits
- To inhibit local recurrence in dogs with incompletely resected soft tissue sarcomas
- Antineoplastic
- Immunosuppressant (IMHA/ITP)
- Immunosuppressant (IMHA pulse therapy)
- Polyarthritis
- Glomerulonephritis
- Lymphoma (COP low dose protocol - Induction)
- Lymphoma (COP low dose protocol - Maintenance after 2 months)
How it is given
Possible side effects
- Myelosuppression (leukopenia, thrombocytopenia, anemia)
- Gastroenterocolitis (anorexia, nausea, vomiting, diarrhea)
- Sterile hemorrhagic cystitis (induced by acrolein metabolite)
- Alopecia (especially in continuously growing coats like Poodles and Old English Sheepdogs)
- Pulmonary infiltrates and fibrosis
- Hyponatremia
- Secondary leukemia
- Myelosuppression (nadir usually 5-14 days post-therapy)
- Sterile haemorrhagic cystitis (caused by acrolein metabolite)
- Bladder fibrosis
- Transitional cell carcinoma (secondary to chronic cystitis)
- Vomiting
- Diarrhoea
Cautions & contraindications
- Prior anaphylactic reactions to the drug
- Severe pre-existing myelosuppression (leukopenia, thrombocytopenia)
- Active infections where immunosuppression may be dangerous
- No specific contraindications available in the monograph, but clinically contraindicated in patients with severe pre-existing myelosuppression or active haemorrhagic cystitis.
- Pre-existing severe myelosuppression
- Active haemorrhagic cystitis
- **WARNING**: Cyclophosphamide is potentially teratogenic and embryotoxic. Safe use in pregnancy is not established. * **Hemorrhagic Cystitis**: Up to 30% of dogs on long-term therapy may develop sterile hemorrhagic cystitis. Encourage frequent urination and water intake. Co-administration of furosemide may reduce risk. * **Myelosuppression**: Monitor CBC closely. Delay doses if severe leukopenia or thrombocytopenia occurs. * **Handling**: Cytotoxic precautions must be taken. Do not split or crush tablets. Avoid direct contact with urine or feces of treated animals.
Drug interactions
- Allopurinol: May increase the myelosuppression caused by cyclophosphamide
- Doxorubicin: Potentiation of cardiotoxicity may occur
- Chloramphenicol: May inhibit cyclophosphamide metabolism
- Phenobarbital: May increase the rate of metabolism to active metabolites, increasing toxicity risk
- Thiazide Diuretics: May increase the myelosuppression caused by cyclophosphamide
- Succinylcholine: Metabolism may be slowed, prolonging effects due to decreased pseudocholinesterases
- Digoxin: Absorption of orally administered digoxin may be decreased (may occur several days after dosing)
- Barbiturates: Increase cyclophosphamide toxicity due to increased rate of conversion to metabolites
- Phenothiazines: Reduce cyclophosphamide efficacy
- Ondansetron: Reduce cyclophosphamide efficacy
- Insulin: Insulin requirements are altered by concurrent cyclophosphamide
Frequently asked questions
What is Cyclophosphamide used for in pets?
> **Important Safety Warning**: This is a potent chemotherapy drug. Follow all handling instructions carefully. * **Handling**: Do not break or crush tablets. Wash hands thoroughly after handling. Avoid direct contact with your pet's urine, feces, or vomit while they are on this medication. * **Urination**: Take your dog for frequent walks to encourage urination, especially in the morning. This helps prevent bladder irritation. * **When to call the vet**: Contact your veterinarian immediately if you notice blood in the urine, straining to urinate, abnormal bleeding, bruising, severe lethargy, vomiting, or diarrhea.
Is Cyclophosphamide safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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