**Question:** Zidovudine causes:

**Core Concept:** Zidovudine is an antiretroviral drug commonly used in the treatment of HIV infection. It belongs to the class of drugs known as nucleoside reverse transcriptase inhibitors (NRTIs), which interfere with the replication of the HIV virus by inhibiting the reverse transcriptase enzyme.

**Why the Correct Answer is Right:** Zidovudine acts as a competitive inhibitor of the reverse transcriptase enzyme, which is essential for the HIV virus to replicate its genetic material. By occupying the enzyme's active site, zidovudine prevents the binding of the viral RNA to DNA, thus inhibiting the conversion of viral RNA to DNA, ultimately blocking the replication of the HIV virus.

**Why Each Wrong Option is Incorrect:**

A. Incorrect: Zidovudine's mechanism of action is not related to interfering with the activity of CD4+ T cells, which are primarily affected by HIV infection.

B. Incorrect: Although zidovudine may cause some degree of myelosuppression, the primary action of the drug is centered around inhibiting the HIV virus's replication rather than affecting the host's immune system.

C. Incorrect: Zidovudine does not primarily cause liver toxicity as its primary action is focused on inhibiting the HIV virus, not affecting liver function.

D. Incorrect: Although zidovudine may cause some degree of neuropathy, the primary action of the drug is centered around inhibiting the HIV virus's replication rather than affecting the nervous system.

**Clinical Pearl:** Zidovudine is a crucial component of combination antiretroviral therapy (ART) for HIV-infected patients, improving survival rates and reducing the progression of HIV infection to AIDS. However, it's essential to monitor patients for potential adverse effects like myelosuppression, liver toxicity, and neuropathy.

**Correct Answer:** D. Zidovudine causes neuropathy, as one of the side effects of the drug is peripheral neuropathy, which is a consequence of its primary action in inhibiting HIV replication.