 [ Symptoms ] i used sandoz brand fentanyl patches and they worked well my pharmacy switched me to mylan is there a preferred brand  they appear to be totally different looking    you cannot see the liquid medication inside as you could with the sandoz when i put the sandoz brand on i could immediately feel a rush and a funny taste in my mouth they began to work in about 45 minutes and the mylan do not seem to work as fast is there a difference in brands both were 75 mcgh i have been using the patches for about eight weeks [ Disease ] most helpful answer you may have been experiencing a niacin flush from taking a bit more niacin than your body could process