Yes, I guess it must be a shock. It's called, among patients, "poop-out". Many doctors don't believe it happens. You've probably found one who has seen it happen. It may be related to some mechanism whereby the body develops resistance to the drug, but that is only one theory. Another is that the body changes over time, as does the illness so that what worked for some time, has to change. That's the gloomy part. But this doesn't happen to everyone. Many people are on one med for decades and they never poop out. The other thing is that there are enough meds out there (and more being developed all the time) that your chances of finding quite a few for you are good. When taking combinations, they interact with each other so the same drug may behave differently with other combinations, so there are more possibilities there too. Are you in therapy? Meds AND therapy are like 1+1=3. CBT is one technique that has been proved in clinical trials. Once you are in remission, enjoy that time without worrying about how long it will last. It may last many years. If it fails, there'll always be something else down the line.