A client with cancer has been receiving the oprelvekin (Neumega). Which of the following laboratory results best indicates that the drug is not having the desired effect and further evaluation is necessary? A. An increase in WBC to 14,000 cells \(/ \mathrm{mm}\) B. A drop in hematocrit to \(29 \%\) C. An increase in cretinine level to \(4.2 \mathrm{mg} / \mathrm{dL}\) D. A drop in platelet count to \(50,000 \mathrm{~mm}\)

Oprelvekin (Neumega) is a medication used to prevent or reduce thrombocytopenia (low platelet count) in patients receiving chemotherapy for cancer. The drug works by stimulating the production of platelets in the bone marrow. Therefore, if the drug is not effective, we would expect to see a decrease in platelet count or other factors related to platelet production or function.

Let's examine each given laboratory result and determine if it is likely to indicate a problem with the drug. A. An increase in WBC (white blood cells) to 14,000 cells/mm^3 - This may indicate an infection or inflammation, but it is not directly related to platelet function or production. It is not a strong indicator that the drug is not effective. B. A drop in hematocrit to 29% - Hematocrit is the volume percentage of red blood cells in the blood. A decrease in hematocrit may indicate anemia, but it is not directly related to platelets and their function, so this result is not a strong indicator that the drug is not effective. C. An increase in creatinine level to 4.2 mg/dL - Creatinine is a waste product produced by muscles and excreted through the kidneys. Increased creatinine levels may indicate kidney problems, but this result is not directly related to platelet production or function. It is not a strong indicator that the drug is not effective. D. A drop in platelet count to 50,000/mm^3 - A drop in platelet count, especially to a level this low, is a clear sign that the drug may not be effective in preventing thrombocytopenia. This result directly indicates a problem with the drug's main purpose, which is to stimulate platelet production.

Based on the analysis above, option D (a drop in platelet count to 50,000/mm^3) is the laboratory result that best indicates that the drug is not having the desired effect, and further evaluation is necessary.