Allopurinol potentiates action of
**Core Concept**
Allopurinol is a xanthine oxidase inhibitor used in the management of gout and hyperuricemia. It works by inhibiting the enzyme xanthine oxidase, which is involved in the production of uric acid. By inhibiting this enzyme, allopurinol reduces the production of uric acid and increases its excretion.
**Why the Correct Answer is Right**
The correct answer is **C. Folinic acid**. Allopurinol potentiates the action of folinic acid because it increases the levels of 5-phosphoribosyl-1-pyrophosphate (PRPP), a precursor for purine synthesis. Folinic acid, a derivative of folic acid, is then converted to tetrahydrofolic acid, which is necessary for the synthesis of nucleic acids. The increased levels of PRPP and tetrahydrofolic acid enhance the effectiveness of folinic acid in promoting nucleic acid synthesis.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because allopurinol does not directly interact with warfarin, an anticoagulant.
* **Option B:** This is incorrect because allopurinol does not potentiate the action of aspirin, a nonsteroidal anti-inflammatory drug (NSAID).
**Clinical Pearl / High-Yield Fact**
It's essential to remember that allopurinol can increase the risk of hypersensitivity reactions, particularly in patients with a history of allergic reactions. Patients should be monitored closely for signs of hypersensitivity, such as rash, fever, and eosinophilia.
**Correct Answer: C. Folinic acid**