Paper II
2013 April (2010 Scheme) · 40 marks · 120 min

Question

Cyclophosphamide

Q43 marksShort Notes

Answer

Cyclophosphamide is an alkylating agent used as an anticancer and immunosuppressant drug.

Mechanism of action

  • A prodrug, activated in the liver by microsomal enzymes (CYP450) to phosphoramide mustard, the active alkylating metabolite
  • Alkylates DNA (cross-links guanine bases), preventing DNA replication and transcription — cell-cycle non-specific

Uses

  • Malignancies: lymphomas, leukaemias, multiple myeloma, breast cancer, various solid tumours
  • Immunosuppression: nephrotic syndrome, rheumatoid arthritis, SLE, vasculitis (e.g., Wegener’s granulomatosis)
  • Conditioning regimen before bone marrow transplantation

Adverse effects

  • Haemorrhagic cystitis — due to the toxic metabolite acrolein; prevented by adequate hydration and mesna (which detoxifies acrolein in the urinary tract)
  • Myelosuppression (leukopenia)
  • Alopecia
  • Nausea, vomiting
  • Gonadal toxicity/infertility
  • SIADH (with high doses)
  • Cardiotoxicity (very high doses), secondary malignancy (long-term)

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