Effects of Intravenous and Oral Magnesium on Reducing Migraine: A Meta-analysis of Randomized Controlled Trials. Pain Physician 2016

"...CONCLUSIONS: Intravenous magnesium reduces acute migraine attacks within 15 – 45 minutes, 120 minuts, and 24 hours after the initial infusion and oral magnesium alleviates the frequency and intensity of migraine. Intravenous and oral magnesium should be adapted as parts of multimodal approach to reduce migraine."
read more: https://www.ncbi.nlm.nih.gov/pubmed/26752497