A nurse is monitoring a client who is receiving morphine IV and amitriptyline PO. Which of the following findings indicates an adverse interaction between the prescribed medications?

A. Low-grade fever: A mild fever is not typically associated with the interaction between morphine and amitriptyline. It may indicate an unrelated infection or inflammatory process rather than a medication effect. B. Urinary retention: Both morphine (an opioid) and amitriptyline (a tricyclic antidepressant) have anticholinergic properties that can decrease bladder tone and inhibit urination. When combined, they increase the risk of urinary retention, making this a significant adverse interaction. C. Diarrhea: These medications more commonly cause constipation rather than diarrhea because of their combined effects on slowing gastrointestinal motility. Diarrhea would not indicate an interaction between the two drugs. D. Tachypnea: Morphine typically causes respiratory depression rather than an increased respiratory rate. Tachypnea would not be a sign of interaction but could occur as a compensatory response to pain or anxiety.