Rehabilitation Physicians, PC Offers Botox for Migraines Used in Tiny Doses in Specific Areas, It Temporarily Reduces Muscle Contractions for Approximately 3 Months. The FDA Approves the Use of Botox to Treat Chronic Migraines in Adults Who Are Age 18 or Over. About 1% to 2% of peoplehave chronic migraines, which means they get migraine-like headaches 15 or more days every month for at least 3 months. Botox is preventive medicine and can help to stop a migraine headache before it starts. Botox is injected around pain fibers that are involved in headaches. Botox enters the nerve endings around where it is injected and blocks the release of chemicals involved in pain transmission. This prevents the activation of pain networks in the brain. In studies, Botox prevented about 8 to 9 headache days a month, compared to 6 to 7 days per month for patients given a placebo, an inactive treatment.