Levothyroxine (LT4) and proton pump inhibitors (PPI) are two of the most prescribed drugs particularly in elderly population [1,2]. As they are frequently co-ingested, the effect on levothyroxine absorption is especially relevant due to its narrow therapeutic index [1]. It is well established that an acid gastric pH is required to the dissolution of LT4 before its absorption in the intestine. Accordingly, some in vitro studies illustrated that an increase in the gastric pH affects the dissolution of the LT4 tablet [3].
