Which medication is known to cause bone marrow suppression as a side effect?

• A. Methotrexate
• B. Acetaminophen
• C. Acetylcysteine
• D. Tamoxifen

Answer: (A)

Methotrexate is an antimetabolite that inhibits dihydrofolate reductase, blocking the production of purines and thymidylate needed for DNA synthesis. Because bone marrow cells divide rapidly, they are particularly affected, leading to myelosuppression with decreased red cells, white cells, and platelets. This myelosuppressive effect is a well-known limiting toxicity that requires careful monitoring of blood counts during therapy. By contrast, acetaminophen mainly risks liver injury at high doses, and acetylcysteine is used to treat acetaminophen overdose rather than causing bone marrow suppression. Tamoxifen’s common adverse effects relate to estrogen receptor modulation, such as hot flashes or thromboembolic risk, rather than bone marrow suppression. So the medication most associated with bone marrow suppression is methotrexate.