A client with chemotherapy induced nausea receives a prescription for metoclopramide. Which adverse effect is most important for the nurse to report?

A. Unusual irritability: While irritability can occur with many medications, it is not a hallmark sign of serious toxicity with metoclopramide. This finding may warrant monitoring but is not the most urgent adverse effect to report. B. Nausea: Persistent nausea may suggest inadequate therapeutic response but is not an immediate safety concern. It can be addressed by adjusting antiemetic therapy without requiring urgent discontinuation. C. Diarrhea: Diarrhea is a common gastrointestinal side effect of metoclopramide but is usually self-limiting. It is not considered life-threatening unless severe dehydration develops, so it is not the most critical finding. D. Involuntary movements: Metoclopramide can cause extrapyramidal symptoms, including dystonia, akathisia, and tardive dyskinesia. These involuntary movements can become permanent if not addressed promptly, making this the most urgent adverse effect to report.