Hemorrhagic Cystitis Sterile hemorrhagic cystitis, a side effect of chemical irritation to the bladder from cyclophosphamide, can be decreased and often prevented by promoting a liberal fluid intake frequen voiding immediately after feeling the urge, before bed, and after arising administering the drug carly in the day to allow for sufficient oral intake and voiding and administering mesna as ordered. If oral home administration is prescribed, the family need specific instructions regarding exactly how much fluid the child must have.