Section 07 · Monograph
Cyclophosphamide
Reviewed Nov 2026FDA label
CytoxanAlkylating immunosuppressant
- Forms
- Tab: 25, 50mg | Cap: 25, 50mg | IV: 500mg, 1g, 2g vials
- Dose
- Refractory MG, NMOSD, CNS vasculitis (off-label): IV 500-1000mg/m² monthly, or oral 1-2mg/kg/day
- MOA
- DNA crosslinking; depletes proliferating lymphocytes
Indications
- Malignant lymphomas, leukemias, multiple myeloma, breast and ovarian cancers, neuroblastomaFDA-labeled
- Minimal change nephrotic syndrome in pediatric patients (oral)FDA-labeled
Off-Label Uses
- Refractory myasthenia gravisOff-label
- NMOSD, CNS vasculitis, CIDP and neuropsychiatric lupusOff-label
Mechanism of Action
- Prodrug activated by hepatic CYP enzymes to phosphoramide mustard, an alkylating agent that crosslinks DNA and depletes proliferating lymphocytes
Full Dosing
Adult / usual
- Neuroimmunology (off-label): IV pulses 500-1000mg/m² monthly (often with mesna), or oral 1-2mg/kg/day
- Maintain hydration and frequent voiding to reduce hemorrhagic cystitis risk
Renal
- Adjust for renal impairment and myelosuppression
Contraindications
- Urinary outflow obstruction
- Severe hypersensitivity to cyclophosphamide or its metabolites
Drug Interactions
- Allopurinol and thiazides increase myelosuppression
- CYP2B6/3A4 inducers (phenytoin, carbamazepine, rifampin) increase active metabolite exposure
- Avoid live vaccines
Adverse Effects
- Myelosuppression and infection
- Hemorrhagic cystitis
- Nausea and vomiting, alopecia
- Infertility and gonadal toxicity
- Secondary malignancy (bladder, hematologic); cardiotoxicity at high doses
Monitoring Parameters
- CBC with differential, urinalysis for hematuria
- Renal function and hydration
- Infection prophylaxis and fertility counseling
Pregnancy & Lactation
- Teratogenic — avoid in pregnancy; use effective contraception during and after treatment
- Breastfeeding contraindicated