Final answer:
A nurse should instruct a client starting sumatriptan to monitor for and report chest pain and tightness, as these are potential adverse effects of the medication.
Step-by-step explanation:
When a nurse is providing teaching to a client on how to start taking sumatriptan, the nurse should instruct the client to monitor for and report severe or concerning adverse effects, such as chest pain and tightness. Sumatriptan, a medication used for the treatment of migraines, can have cardiovascular side effects due to its vasoconstrictive properties, which can lead to symptoms such as chest pain or a sensation of tightness. It is important for patients to be aware of these potential side effects to ensure prompt medical attention if they occur.