## **Core Concept**
Peripheral neuritis, a side effect of isoniazid, is related to its interference with vitamin B6 (pyridoxine) metabolism. Isoniazid forms a hydrazone with pyridoxal phosphate, which is the active form of vitamin B6. This interaction leads to a decrease in the availability of pyridoxal phosphate, an essential coenzyme for various enzymatic reactions, including those involved in neurotransmitter synthesis and myelin maintenance.

## **Why the Correct Answer is Right**
The correct answer, , involves the formation of a complex between isoniazid and pyridoxal phosphate (or vitamin B6), leading to the depletion of pyridoxal phosphate. This depletion disrupts the synthesis of neurotransmitters and the maintenance of the myelin sheath, resulting in peripheral neuritis. The reaction involves the condensation of isoniazid with pyridoxal to form a hydrazone, which is then excreted. This mechanism explains why supplementation with pyridoxine can prevent or treat isoniazid-induced peripheral neuritis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option does not accurately represent the mechanism by which isoniazid causes peripheral neuritis.
- **Option B:** Similarly, this option does not correctly describe the formation of a complex relevant to isoniazid-induced neuritis.
- **Option D:** This option also does not accurately depict the mechanism of isoniazid-induced peripheral neuritis.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that patients on isoniazid therapy should be supplemented with pyridoxine (vitamin B6) to prevent peripheral neuropathy, especially if they are at high risk (e.g., pregnant women, patients with pre-existing neuropathy, or those with poor nutritional status). This preventive measure can significantly reduce the incidence of this side effect.

## **Correct Answer:** .