Myelo means bone marrow, and myelosuppression is the process in which we intentionally suppress the bone marrow to decrease the white cell count below a certain value. Drugs used for this purpose include busulfan and hydroxyurea. This is by no means a cure, and the effect is temporary, but it can be life-saving in some cases where the white blood cell count is too high as in a blast crisis, which increases the viscosity of the blood and causes problems like breathlessness, heart attacks and priapism -a sustained penile erection that can potentially cause gangrene in the penis with severe pain-. A rapid reduction of white blood cell count is therefore necessary.
However, the main side effect of this process is that it is hardly controllable and the risk of going too far and causing severe suppression is always present.