Imitrex Imitrex can help to relieve these symptoms much sooner than if the migraine headache went untreated when it can last for up to seventy-two hours. http://www.hawaiianhospitalitygroup.com/ - imitrex pills There is no limit to the number of cluster headaches that a person can experience in one day and each headache can last three hours or more. Imitrex is a prescription drug used to treat migraine and cluster headaches.