I just took it recently and when I was younger I had zero problem with it. But now.. OMG... it set off a terrible panic attack. I was only on 15 mg. I stopped it completely. When I was younger Phentermine didn't work because it would wear off about 13 weeks in. But i had been hoping to use it in a different way. I was going to diet for 13 weeks,, stop maintain and then go back at it again.