## Core Concept
Isoniazide is a first-line antitubercular medication that requires understanding of its metabolism to appreciate its pharmacokinetics and potential drug interactions. The metabolism of isoniazide involves specific enzymatic pathways.

## Why the Correct Answer is Right
Isoniazide is primarily metabolized by **acetylation**, specifically through the enzyme **N-acetyltransferase 2 (NAT2)**. This process converts isoniazide into its major metabolite, **acetylisoniazid**. The rate of acetylation categorizes individuals into **slow acetylators** and **fast acetylators**, influencing the drug's plasma levels and half-life. Slow acetylators have higher risks of toxicity, while fast acetylators may have reduced efficacy due to lower drug levels.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not specify the correct metabolic pathway or enzyme involved in isoniazide metabolism.
- **Option B:** This option is incorrect as it does not accurately represent the primary metabolic pathway for isoniazide.
- **Option D:** This option is incorrect because it does not correctly identify the enzyme or process responsible for isoniazide's metabolism.

## Clinical Pearl / High-Yield Fact
A key clinical point to remember is that the acetylation status of individuals can influence the dosing and effectiveness of isoniazide. **Slow acetylators** are at a higher risk of developing **peripheral neuropathy** and other toxicities, and may require dose adjustment to avoid toxicity while maintaining efficacy.

## Correct Answer: C. Acetylation.