Before administering the initial dose of sumatriptan succinate to a client with a migraine headache, it is most important to determine if the client's history includes which problem?

A. Sumatriptan is a triptan used to treat migraines, but it can cause vasoconstriction, which may exacerbate coronary artery disease. Therefore, it is crucial to assess for a history of this condition before administration. B. Irritable bowel syndrome does not significantly impact the use of sumatriptan. C. Seasonal allergic rhinitis is not a contraindication for sumatriptan use. D. Type 2 diabetes mellitus is not a contraindication for sumatriptan use, though blood glucose levels should be monitored as part of overall management.