Final answer:
Patients taking promethazine for cholecystitis-related nausea should report urine retention as an adverse effect, as it may indicate a serious complication and requires immediate medical attention.
Step-by-step explanation:
Promethazine (Phenergan) is commonly used to treat nausea and vomiting and has antihistaminic properties. However, this medication can also cause a variety of adverse effects. Patients taking promethazine should be instructed to report certain side effects that can indicate serious complications. Among the listed options, urine retention is the most concerning and medically significant side effect that should be promptly reported to a healthcare provider. While diarrhea, insomnia, and dry mouth can occur with promethazine use, urine retention may be a sign of a more severe problem such as urinary tract obstruction or other urinary system dysfunction and, therefore, requires immediate medical attention.
When educating patients about promethazine usage, especially for conditions related to the digestive system like cholecystitis, it is crucial to provide comprehensive information on potential side effects to ensure patient safety and prompt intervention when necessary.