This is true for over-the-counter medications like Excedrin and BC powders, as well as prescription medications like Fiorinal, Midrin, and “triptans” like Imitrex, Zomig, Relpax
, etc. Exactly why this occurs is unclear, but it is a well established clinical finding. Anyone who takes pain medications more than twice a week is in danger of perpetuating their headaches. Occasional usage of pain medications several times in one week is permissible, as long as it is not a regular pattern.