<s>[INST] context: Cyclophosphamide Hemorrhagic cystitis is commonly associated with Cyclophosphamide Cyclophocphamide is the most common cause of hemorrhagic cystitis. The drug Cyclophosphamide itself is not toxic. The drug toxicity is due to its hepatic conversion to the metabolite "acrolein" which is excreted in the urine and causes damage to the bladder mucosa - It is believed that urothelial damage occurs due to direct contact of the bladder wall with acrotein which causes edema, ulceration, neovascularisation, hemorrhage and necrosis - Thus patients receiving cyclophosphamide should always receive good hydration and a .foley's catheter is often placed to ensure immediate drainage of the bladder. The hemorrhagic cystitis caused by cyclophosphamide can be reduced in intensity or prevented by intravenous administration of "MESNA" -MESNA is a thiol compound. The .free (Thiol) groups of MESNA combine directly with double bond of acrolein of form a stable nontoxic compound. MESNA is given orallyQ. - Cyclophosphamide induced hemorrhagic cystitis appeare to be dose related and is most prevalent in patients who are dehydrated and those receiving intravenous cyclophosphamide. [/INST] question: Hemorrhagic cystitis is caused by aEUR' | options: A: Busulphan B: Cisplatin C: Cyclophosphamide D: Doxorubicin | answer: C </s>