<prompt> Haemorrhagic cystitis is caused byCyclophosphamideBusulphanPrednisoloneMelphalan  <response>: Ans. is a i.e., Cyclophosphamide Hemorrhagic cystic is most commonly associated with cyclophosphamide seen in 5-10 of patients.In Harrison drugs causing hemorrhagic cystitis have been listed and this also includes Busulphan.Still, I prefer cyclophosphamide as the answer because none of the pharmacology books This even includes Goodman Gilman mention hemorrhagic cystitis as an adverse effect of Busulfan.More question on this topic: -Hemorrhagic cystitis has been attributed to cyclophosphamide because of the presence of acrolein.Adequate hydration and intravenous injection of MESNA Sodium 2-mercaptoethane sulfonate minimize this problem. 