A patient undergoing vinblastine chemotherapy is assessed at the end of treatment. Which change is most likely?

• A. Decreased number of neutrophils
• B. Increased serum glucose concentration
• C. Increased hematocrit
• D. Increased activated partial thromboplastin time

Answer: (A)

Chemotherapy drugs that disrupt division in rapidly renewing tissues commonly cause bone marrow suppression. Vinblastine inhibits microtubule formation, blocking mitosis in marrow progenitors, so neutrophil production drops. Neutrophils have a short lifespan and rely on constant marrow output, making a decrease in neutrophil count the most likely end-of-treatment change. Other options aren’t as directly tied to this drug’s toxicity: glucose can rise with stress or steroids but isn’t the hallmark effect here; hematocrit would more likely fall with anemia rather than rise; and prolonged APTT would indicate a coagulation issue not typical of vinblastine therapy.