Cyclophosphamide (Nephrology)

How it works

Its active metabolites cross-link DNA, impairing replication of rapidly dividing cells including activated lymphocytes, producing potent immunosuppression.

Prescribing in practice

• Acrolein metabolites cause haemorrhagic cystitis and bladder toxicity; ensure good hydration and consider mesna with higher-dose or intravenous regimens, and counsel on long-term bladder malignancy risk.
• It causes bone marrow suppression and infection risk, so monitor blood counts and give appropriate prophylaxis (e.g. against Pneumocystis); doses are reduced in renal impairment.
• It is gonadotoxic and teratogenic; discuss fertility preservation and ensure effective contraception, with cumulative dose kept as low as possible.

Monitoring

Monitor full blood count, renal function and urinalysis for haematuria during treatment, with infection surveillance.

Counselling the patient

• Drink plenty of fluids and empty your bladder regularly to protect it; report any blood in the urine.
• Seek urgent advice for fever or signs of infection, as your immune system is suppressed.
• Use reliable contraception and discuss fertility before starting, as this drug can affect fertility and harm a pregnancy.

Evidence & guidelines

Cyclophosphamide-based induction is established for organ- or life-threatening ANCA-associated vasculitis and proliferative lupus nephritis, supported by trials such as CYCLOPS and the Euro-Lupus regimens.