Alkylating agent / immunosuppressant Pregnancy: Use during pregnancy, particularly first trimester, is not recommended (reports of serious multiple congenital aberrations; teratogenic in animals). Women should not conceive during and for 12 months after therapy; men should not father a child during and for 6 months after therapy. Contraindicated during breastfeeding.

Cyclophosphamide

Brand names: Endoxana

Cyclophosphamide is a nitrogen-mustard alkylating cytotoxic agent used as an immunosuppressant in severe autoimmune and rheumatological disease (such as systemic vasculitis and lupus) and as chemotherapy in various malignancies.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Haematologic and solid tumours: for intermittent treatment 10-15 mg/kg body weight (= 400-600 mg/m2 BSA), with therapy-free intervals of 2 to 5 days

Route: Intravenous (injection/infusion)

Frequency: Intermittent, with therapy-free intervals of 2-5 days (regimen-dependent)

Max: Not stated as a single fixed cap in §4.2 (dose is individualised)

Dosage must be individualised; doses/duration/intervals depend on indication, combination scheme, general health, organ function and lab monitoring. General guidelines (all IV): daily treatment 3-6 mg/kg (=120-240 mg/m2); intermittent 10-15 mg/kg (=400-600 mg/m2) every 2-5 days; high-dose intermittent 20-40 mg/kg (=800-1600 mg/m2) every 21-28 days. Bone marrow transplant preparation: 60 mg/kg IV for 2 days or 50 mg/kg IV for 4 days. Autoimmune diseases: 500-1000 mg/m2 per month. If busulfan-cyclophosphamide (Bu/Cy) regimen, first cyclophosphamide dose at least 24 h after last busulfan dose. Force diuresis with adequate fluid before/during/after; administer in the morning. Dose adjustment for myelosuppression: full dose if leukocytes >=4000/uL and platelets >=100,000/uL; 50% dose if leukocytes 2500-4000 or platelets 50,000-100,000; omit if below. Use only under a specialist oncology service by clinicians experienced in cancer chemotherapy. Paediatric: cyclophosphamide has been administered to children; safety profile similar to adults; no discrete per-kg paediatric regimen stated in this SPC section.

Dose adjustments

Renal

Decreased renal excretion may increase plasma levels and toxicity; a dose reduction of 50% is recommended for GFR below 10 mL/min. Cyclophosphamide and metabolites are dialyzable.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to cyclophosphamide or any of its metabolites
Acute infections
Bone marrow aplasia or bone marrow depression prior to treatment
Urinary tract infection
Acute urothelial toxicity from cytotoxic chemotherapy or radiation therapy
Urinary outflow obstruction
Breastfeeding
Should not be used in non-malignant disease except for immunosuppression in life-threatening situations

Side effects

Myelosuppression / leukopenia / neutropenia (very common)
Febrile neutropenia (common)
Immunosuppression with severe, sometimes fatal, infections (very common)
Alopecia, nausea, vomiting, diarrhoea (reported most often)
Haemorrhagic cystitis and urinary tract/renal toxicity

Interactions

Protease inhibitors: may increase cytotoxic metabolite concentrations and enhance toxicities (infections, neutropenia, mucositis) [US label]
Radiation therapy or drugs with similar toxicities: potentiate myelosuppression, nephrotoxicity, cardiotoxicity, pulmonary toxicity, hepatotoxicity [US label]
Metronidazole: acute encephalopathy reported [US label]
Busulfan (Bu/Cy regimen): timing of doses must be separated (see notes)

Clinical monograph

How it works

It is a prodrug metabolised in the liver to active alkylating species (including phosphoramide mustard) that cross-link DNA strands, impairing replication and inducing apoptosis in rapidly dividing and immune cells.

Prescribing in practice

It is toxic to the bladder urothelium (haemorrhagic cystitis) and carries a long-term risk of bladder cancer, so adequate hydration and, with higher exposures, mesna uroprotection are used.
Causes bone marrow suppression, increased infection risk, infertility and is teratogenic.
A cumulative-dose-limited cytotoxic that must be prescribed under specialist supervision in line with the SPC and disease-specific protocols.

Monitoring

Monitor full blood count, renal and hepatic function and urinalysis for haematuria, with maintained hydration around administration.

Counselling the patient

Maintain a good fluid intake and empty the bladder regularly; report any blood in the urine.
Report fever or other signs of infection without delay.
Discuss fertility preservation before treatment and use effective contraception, as the drug can harm a pregnancy.

Evidence & guidelines

Its use in severe vasculitis and lupus is supported by long-standing trial evidence and current rheumatology guidance, alongside the SPC.

Reference: EULAR; BSR vasculitis; KDIGO; ESMO; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways