Just to add my experience, I did two Clen cycles last year, and while the typical side-effects were barely noticable, my resting pulse (e.g., in bed) went up to 95-100 BMP! I felt fine, but obviously my heart was working in overdrive - constantly. It freaked me out and I decided that it's just not for me. Common sense suggested that having my heart have to work that hard couldn't be doing me any good. Too bad, though, I did enjoy the boost it gave me while dieting.
ebear