**Core Concept**
The prevention of mother-to-child transmission (PMTCT) of HIV involves administering antiretroviral drugs to pregnant women and their newborns. Nevirapine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in combination with other antiretroviral agents for PMTCT.

**Why the Correct Answer is Right**
Nevirapine is administered to the newborn as a single dose at birth (4 mg/kg) to prevent HIV transmission. This dose is sufficient to inhibit HIV replication in the newborn's cells. The mechanism of action involves binding to the HIV reverse transcriptase enzyme, thereby preventing viral replication. The correct dose is essential to ensure efficacy while minimizing toxicity.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the recommended dose for newborns is not 2 mg/kg.
* **Option B:** This option is incorrect because the recommended dose for newborns is not 6 mg/kg.
* **Option C:** This option is incorrect because the recommended dose for newborns is not 8 mg/kg.

**Clinical Pearl / High-Yield Fact**
When administering Nevirapine to newborns for PMTCT, it is essential to ensure accurate dosing to prevent toxicity while maintaining efficacy.

**Correct Answer:** D. 4 mg/kg