Hemorrhagic cystitis is caused by
**Core Concept**
Hemorrhagic cystitis is a condition characterized by bleeding from the bladder mucosa, leading to hemorrhage and cystitis. This condition is often caused by chemical injury to the bladder mucosa, which can be due to certain medications or infections.
**Why the Correct Answer is Right**
The correct answer is cyclophosphamide, a chemotherapeutic agent that belongs to the class of nitrogen mustard alkylating agents. Cyclophosphamide is metabolized by the liver enzyme cytochrome P450 to form acrolein, a toxic metabolite that causes damage to the bladder mucosa, leading to hemorrhagic cystitis. This is a well-documented side effect of cyclophosphamide, and patients receiving this medication are often advised to drink plenty of fluids to prevent this complication.
**Why Each Wrong Option is Incorrect**
**Option A:** Ifosfamide is another chemotherapeutic agent that can cause hemorrhagic cystitis, but it is not the correct answer. While ifosfamide also metabolizes to acrolein, the question is asking for a single answer, and ifosfamide is not the most commonly associated agent with this condition.
**Option B:** Cisplatin is a chemotherapeutic agent that can cause renal toxicity, but it is not typically associated with hemorrhagic cystitis.
**Option C:** Gemcitabine is a chemotherapeutic agent that can cause renal toxicity and other side effects, but it is not commonly associated with hemorrhagic cystitis.
**Clinical Pearl / High-Yield Fact**
When prescribing cyclophosphamide, it is essential to advise patients to drink plenty of fluids to prevent hemorrhagic cystitis. This can be remembered using the mnemonic "CYP" - cyclophosphamide, hydration, and prophylaxis (using medications like mesna to prevent cystitis).
**Correct Answer: C. Cyclophosphamide**