Final answer:
The nurse should closely monitor for respiratory depression in a client who has overdosed on amitriptyline, as it is one of the most serious adverse effects of this medication in such a situation.
Step-by-step explanation:
A nurse is caring for a client who has admitted following an overdose of amitriptyline. Amitriptyline is a tricyclic antidepressant which can cause a variety of side effects. In the context of an overdose, one of the most critical adverse effects the nurse should monitor is respiratory depression. While normal therapeutic doses might cause drowsiness and slight decreases in blood pressure among other symptoms, an overdose significantly increases the risk of serious side effects like respiratory depression, abnormal heart rhythms, and low blood pressure. These effects stem from the drug's impact on the central nervous system and the cardiovascular system.
The risk of respiratory depression becomes more pronounced with higher doses, which can lead to decreased respiratory function and even death. Therefore, the nurse's priority in monitoring would include keeping a close watch on the client's respiratory status, assessing for any signs of decreased respiratory effort, or abnormal breathing patterns.