**Question:** Drugs Supplied by NACO for prevention of mother to child transmission:

A. Nevirapine
B. Zidovudine
C. Lamivudine
D. Tenofovir

**Core Concept:** NACO stands for National AIDS Control Organization, a government agency in India responsible for providing antiretroviral therapy (ART) drugs to prevent mother-to-child transmission (PMTCT) of HIV. These drugs are used to reduce the risk of HIV transmission from infected mothers to their unborn children.

**Why the Correct Answer is Right:** The correct answer, D. Tenofovir, belongs to a class of medications known as NRTIs (Nucleoside/Nucleotide Reverse Transcriptase Inhibitors). Tenofovir is used as part of a combination therapy in HIV treatment, including PMTCT. It works by inhibiting the HIV reverse transcriptase enzyme, preventing the virus from replicating within the host cell. By doing so, it helps reduce the viral load in the mother's body and subsequently decreases the risk of HIV transmission to the child during childbirth or breastfeeding.

**Why Each Wrong Option is Incorrect:**

A. Nevirapine (NVP): NVP is a NNRTI (Non-Nucleoside Reverse Transcriptase Inhibitor). While NVP is used in HIV therapy, it is not typically included in the PMTCT regimen due to its potential side effects and limited protection against vertical transmission compared to Tenofovir.

B. Zidovudine (AZT): AZT is an NRTI, similar to Tenofovir, but its use in PMTCT has been replaced to some extent by Tenofovir due to better efficacy and fewer side effects.

C. Lamivudine (3TC): Lamivudine is another NRTI, like AZT and Tenofovir, but the combination of Tenofovir and Tenofovir Disoproxil Fumarate (TDF) is recommended over Tenofovir monotherapy or Lamivudine monotherapy due to the enhanced efficacy and fewer side effects.

**Clinical Pearl:** NACO, the National AIDS Control Organization in India, provides a combination of antiretroviral drugs for PMTCT. The current standard regimen includes Tenofovir, Lamivudine, and Nevirapine. This combination is known as TDF-3TC-NVP, and it provides better protection against HIV transmission to the child, while minimizing side effects compared to using individual drugs or older regimens. Tenofovir is part of this combination and is essential for reducing the risk of mother-to-child transmission of HIV.