High dose verapamil (more than 240mg a day) for migraine? is this ever employed? my migraines aren't controlled well enough at 240mg.

Very common: The dose should be made on an individual basis, weighing the possible benefit of a higher dose with possible side effect risks. Giving someone more than a maximum of 480 mg per day is not recommended for any type of migraine.

Migraine prevention: Yes, you can try higher doses but we need to monitor your blood pressure & heart rate (don't want either too low are a result of verapamil). And how are your bowels moving? Constipation is common side effect. Have you & your doc considered other options to prevent migraines? 3yrs ago, AAN published prevention guidelines http://alvinblin.blogspot.com/2012/04/evidence-based-migraine-prevention.html

Verapamil: You might ask your Doc if a trial of a different calcium blocker like amlodipine might be worthwhile. Sometimes a combination of beta blocker and calcium blocker helps also. Best to discuss with your doc.