Addiction rarely occurs for migraine use. Once the migraines are better controlled, the opiate is easily discontinued. Magnesium supplementation can help control migraines, but it may take 3-4 months of daily use to see a benefit. It's quite safe as long as there is normal kidney function. The most common form, Magnesium Oxide, is inorganic and may not be well absorbed.
Diarrhea is a sign of poor absorption.
Dosing should start at 400 mg daily and increase to 800 mg daily if tolerated. Migraine in childhood often has atypical features that do not even include headache. Cyclic vomiting in children with no identifiable physical cause is one example. Unexplained recurrent phenomena relieved by sleep, especially if there is migraine in the parents, should be considered for possible migraine. Nasal congestion and watery eyes can be symptoms of migraine.