Final answer:
The client should report chest tightness as an adverse effect of sumatriptan, which is a specific side effect indicating a potentially serious condition. Other side effects such as insomnia and respiratory depression are less specific to sumatriptan.
Step-by-step explanation:
The client who experiences migraine headaches and has a new prescription for sumatriptan should be instructed to report chest tightness to the provider as an adverse effect of this medication. While side effects such as insomnia, photophobia, and respiratory depression may be concerning, chest tightness is specifically associated with sumatriptan and may indicate a serious condition such as coronary vasospasm. Other notable side effects may include symptoms like fatigue, nausea, dizziness, and more severe reactions like seizures or hypertension. It is important for the client to monitor for any unusual symptoms and to communicate effectively with the healthcare provider to ensure proper management of their migraine treatment.