Which of the following is most common side effect of zidovudine?
**Core Concept**
Zidovudine, also known as azidothymidine (AZT), is a nucleoside reverse transcriptase inhibitor (NRTI) used in the treatment of HIV/AIDS. It works by inhibiting the reverse transcriptase enzyme, which is essential for the replication of retroviruses like HIV.
**Why the Correct Answer is Right**
The most common side effect of zidovudine is bone marrow suppression, which leads to anemia, neutropenia, and thrombocytopenia. This is due to the inhibition of DNA synthesis, which affects the rapidly dividing cells in the bone marrow. Zidovudine is phosphorylated to its active form, zidovudine triphosphate, which competes with the natural nucleotides for incorporation into the viral DNA, thereby inhibiting reverse transcription. The inhibition of DNA synthesis also affects the host cells, leading to bone marrow suppression.
**Why Each Wrong Option is Incorrect**
* **Option A:** Nausea and vomiting are common side effects of many antiretroviral medications, but they are not the most common side effect of zidovudine.
* **Option B:** Diarrhea is a common side effect of some antiretroviral medications, but it is not the most common side effect of zidovudine.
* **Option D:** Liver enzyme elevations are a potential side effect of many medications, including some antiretrovirals, but they are not the most common side effect of zidovudine.
**Clinical Pearl / High-Yield Fact**
Bone marrow suppression is a common side effect of many NRTIs, including zidovudine, lamivudine, and stavudine. Regular monitoring of complete blood counts (CBCs) is essential in patients receiving these medications to prevent severe anemia and other hematologic complications.
**Correct Answer: A. Anemia.**