Sumatriptan is a serotonin agonist that acts selectively at 5HT1 receptors. This anti-migraine medication functions by inducing vasoconstriction. CBD acts as an agonist at the human 5-HT1a receptor as well. Since both of these medication function in similar capacities, I would recommend taking one or the other for your migraine pain.
Agonistic properties of cannabidiol at 5-HT1a receptors.
Russo EB, Burnett A, Hall B, Parker KK.
Neurochem Res. 2005 Aug;30(8):1037-43.