no one answered because it's a nonstarter of a question. They are not AB rated so they are obliviously not interchangeable. Macrobid is twice a day and macrodantin is qid. Why would you switch it to macrobid without calling the prescriber changing it to the appropriate dosing schedule (which would lead to better compliance). Macrobid also doesn't come in a 50mg capsule, it's 100mg with 75mg coming from monohydrate and 25mg from macrocrystal