Most chemotherapy drugs work by slowing down or turning off the growth and division machinery inside cells that are rapidly growing and dividing. Since blood cells, which are made in your bone marrow, also grow relatively rapidly, most chemotherapy drugs cause a transient decrease in blood cell counts. These drugs lower the white blood cell count to a greater degree than the counts of other blood cells — red blood cells and platelets — although these are commonly affected, too. Fortunately, the effect of these drugs on the white blood cell count is usually both predictable and short-lived. The white cell count generally falls below the normal range about seven to ten days after a chemotherapy treatment and recovers within about a week after that. Patients are at an increased risk for infection when the white cell count is below normal, so they are counseled to report fever or other changes that may indicate infection, particularly during this more vulnerable period. Sometimes they are given antibiotics at this time to help prevent the development of a severe infection.
The only treatment that has been proved to increase the number of white blood cells after chemotherapy is an injectable medicine that stimulates the bone marrow to make white blood cells faster. There are two such drugs currently available: filgrastim (trade name Neupogen) and pegylated filgrastim (trade name Neulasta). These two drugs cause the white blood cell count to fall a little less, and to recover to normal a little faster. However, neither drug completely stops the white blood cell count from falling below normal, and their use is not appropriate for all patients or for all types of chemotherapy. In fact, many patients are able undergo chemotherapy without lowered white cell counts and therefore don't require Neupogen or Neulasta.
Learn more in the Everyday Health Cancer Center.