Which of the following drug causes additive anaemia and neutropenia if given to an AIDS patient on zidovudine?
**Core Concept**
The question is testing the interaction between two drugs, zidovudine and another medication, which can cause additive hematologic toxicity in an AIDS patient. This is a classic example of pharmacodynamic interaction, where the effects of two drugs are combined to produce an enhanced response.
**Why the Correct Answer is Right**
Zidovudine, a nucleoside reverse transcriptase inhibitor (NRTI), is known to cause bone marrow suppression, leading to anemia and neutropenia. Another drug, ganciclovir, is an antiviral medication used to treat cytomegalovirus (CMV) infections. Ganciclovir also causes bone marrow suppression and can lead to anemia and neutropenia. When given together, these two drugs can cause additive hematologic toxicity, increasing the risk of severe anemia and neutropenia.
**Why Each Wrong Option is Incorrect**
* **Option A:** Trimethoprim-sulfamethoxazole is an antibiotic used to treat various bacterial infections. While it can cause hematologic toxicity, it is not typically associated with additive anemia and neutropenia when given with zidovudine.
* **Option B:** Acyclovir is an antiviral medication used to treat herpes simplex virus infections. It does not typically cause additive hematologic toxicity when given with zidovudine.
* **Option D:** Prednisone is a corticosteroid used to treat various inflammatory conditions. While it can cause hematologic toxicity, it is not typically associated with additive anemia and neutropenia when given with zidovudine.
**Clinical Pearl / High-Yield Fact**
When managing patients on multiple medications, it's essential to be aware of potential pharmacodynamic interactions that can lead to additive toxicity. In this case, the combination of zidovudine and ganciclovir can lead to severe hematologic toxicity, requiring close monitoring and dose adjustments.
**Correct Answer:** C. Ganciclovir