@@aliali- Having a tough time with your switch? This is a superb question. But I think that this depends on the medicine and you. It depends so much on how your metabolism works, what the drugs are and the rate that you switched. Actually there are so many variables I'm not sure anyone can really answer this. As @johnbishop says makes sense- to call your pharmacist or your doctor. Can you tell me the name of the drugs that you switched to and when did you finish the first one>