Botox is actually the only FDA-approved medication for the treatment of chronic migraine. Chronic migraine per the FDA definition is having a history of migraine with headaches 15 or more days a month, lasting four hours at a time. I do consider it to be the first line medication and treatment for chronic migraine, but the limiting factor is insurance companies and their coverage for Botox. Insurance companies typically require the patient to try and fail two or three different classes of preventative medications for migraine before they will approve the Botox. Botox, in my opinion, has fewer side effects compared to oral preventative medications, and I think is well tolerated.
Botox is given in a series of 31 injection every twelve weeks. The sites are across the upper and lower forehead, the sides of the head, the bacK of the head, the upper neck, and in the shoulders.