In hospital a few years ago, I met a man who needed to take anticoagulation medicine daily. However, he had some sort of stomach enzyme that prevented him absorbing the medicine. As a result, daily, an hour beforehand he'd announce he was taking his 'first medicine' and drank a glass of white wine (which the doctors had noted would inhibit the enzyme). (excuse my medical terms, I'm relaying second hand).
Anyway, the question is - if he wants to travel to a dry (as in no alcohol) country, like Iran, or Brunei - could he, if he needs the alcohol? Would a doctor's letter be enough?