**Core Concept**
Isoniazid is a prodrug that requires acetylation to form its active metabolite. The rate of acetylation is genetically determined, with slow acetylators having a slower rate of conversion. This affects the therapeutic efficacy and toxicity of isoniazid.

**Why the Correct Answer is Right**
Slow acetylators of isoniazid are more prone to develop peripheral neuropathy and hepatotoxicity due to higher concentrations of the parent compound. This is because the slower rate of acetylation leads to a longer duration of exposure to the toxic metabolites. The N-acetyltransferase 2 (NAT2) enzyme is responsible for the acetylation of isoniazid, and slow acetylators have a variant of this enzyme that results in a slower acetylation rate.

**Why Each Wrong Option is Incorrect**
* **Option A:** Lactic acidosis is a rare but serious side effect of isoniazid, but it is not more common in slow acetylators.
* **Option B:** Hypersensitivity reactions to isoniazid are not related to the rate of acetylation.
* **Option C:** Pyridoxine deficiency is a risk with isoniazid therapy, but it is not more common in slow acetylators.

**Clinical Pearl / High-Yield Fact**
Slow acetylators of isoniazid are more likely to require lower doses and more frequent monitoring of liver function and peripheral neuropathy.

**Correct Answer:** D. Peripheral neuropathy and hepatotoxicity