Some people say it lowers the effect of ephedrine hcl, but one tab still gives me awesome energy, and I can breath easier during the workouts (I have chronic congestion).
Using ephedrine for direct fat-burning is a waste - not enough direct results, and too much risk of high blood-pressure, etc.
You're much better off using it before HIIT workouts to supercharge the fat loss and metabolism increase (works much better then using ephedrine three times a day just to increase the heart rate), and before gym, like on leg day.