Donna I do not know the reason and believe me I have searched!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! But while on phen the heartburn or throat burn-- I actually never felt the heartburn ---gets so much worse!!!!! You may even find that you have trouble with your throat and swallowing is difficult at times. Also,you may feel as though there is a lump in your throat and thick sticky saliva also.This can become debilitating. I put up with it.......because getting the weight off is important. BUT you must stay regular in the potty too (because phen is constipating) or the reflux is soooooooooooo bad!!! no place for it to go but in your throat.
you may begin to feel as though you have post nasal drip also...Once again..........mylanta is a life saver.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! keep a bottle of pills in your purse and ALWAYS have water in hand. Do not allow the throat burn to get out of control as you know it causes tissue damage that can lead to cancer down the road !!!!!!!! I was miserable with this.Actually scared at times because I couldn't make my throat swallow..Stay on top of this....NEVER don't get your total water in for the day.

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