There have been patients who have been on this drug for 30 years. Because their symptoms are not so severe, it can be used for a very long time. There are some side effects like a drop in sodium level for example, but it can be used for quite a while.
If it's not successful, there are other medications that can be tried like Phenytoin or other drugs in terms of treatment. But we generally find that patients have to add more and more medications to it and it becomes less and less effective. If one medicine fails, the chances of the second one failing increases.
