Hydroxyurea can cause a severe decrease in the number of blood cells in your bone marrow. This may increase the risk that you will develop a serious infection or bleeding.

Why is hydroxyurea toxic?

Hydroxyurea is an extremely toxic drug with a low therapeutic index. Since hydroxyurea inhibits DNA synthesis, it can result in significant toxicity, including myelosuppression. Furthermore, inhibition of DNA synthesis without affecting RNA synthesis may result in red blood cells becoming megaloblastic.

Is hydroxyurea considered a chemotherapy drug?

Hydroxyurea (hydroxycarbamate, Hydrea) is a chemo drug that has helped some patients with CMML live longer. This drug comes as a capsule that's taken by mouth daily. It can bring the numbers of white blood cells and monocytes down to normal. It may also help shrink an enlarged spleen.