## **Core Concept**
The question tests the understanding of the pharmacogenetics of isoniazid, a first-line antitubercular medication. Isoniazid is metabolized by acetylation, a process that affects its plasma levels and toxicity profile. The rate of acetylation categorizes individuals into fast and slow acetylators.

## **Why the Correct Answer is Right**
Slow acetylators have lower activity of the enzyme N-acetyltransferase (NAT), which is responsible for the acetylation and subsequent inactivation of isoniazid. As a result, they maintain higher plasma concentrations of isoniazid for longer periods. This increased exposure to isoniazid is associated with a higher risk of peripheral neuropathy due to the interference with pyridoxine (vitamin B6) metabolism. Isoniazid can lead to pyridoxine deficiency, which is crucial for the synthesis of neurotransmitters and maintaining the health of the nervous system.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While hepatitis is a known side effect of isoniazid, it is not specifically more prevalent in slow acetylators. The risk of hepatitis is more related to the dose and duration of therapy rather than the acetylator status.
- **Option B:** Optic neuritis is a side effect of ethambutol, another antitubercular drug, rather than isoniazid. It is not directly related to the acetylator status.
- **Option C:** This option seems to relate to the correct answer but was not provided. However, based on the context, it can be inferred that it might relate to neuropathy.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that slow acetylators are at a higher risk of developing peripheral neuropathy when taking isoniazid. This risk can be mitigated by the concomitant administration of pyridoxine (vitamin B6). This is a critical consideration in the management of patients on isoniazid, especially in populations known to have a higher prevalence of slow acetylators.

## **Correct Answer:** D. Peripheral neuropathy