The dosages of the phentermine and topamax are actually pretty low for the new medication they're proposing, and phentermine is a pretty weak stimulant anyway.
Topamax is a weird medication. As an anti-convulsant it's decent, as a mood stabilizer for the majority of bipolar folks it's kind of crap, seems to work pretty well as a migraine prevention, and also has some uses addressing nerve disorders. Even though it doesn't work well as a mood stabilizer you often see it as a part of medication regimens because it will help offset weight gain from other meds, usually neuroleptics. A lot of doctors have reported success in using it to help regulate compulsive behavior as well when using it with alcoholics and eating disordered populations.
I started taking topamax last year for migraine prevention and nothing happened except for itchiness for about a week after I hit the dose I ended up staying on (100mg). No cognitive effects, no tingling, no weight loss. Just the non-allergic itching and that went away quickly. But I've seen people who absolutely cannot function on it.
Well, thank you so much for bothering to go to Qnexa's website and finding out just what the hell is in it and analyzing the risks that go along with it. We would have done that ourselves if we weren't so busy dieting and exercising. As commenter DahlELama says, "Nothing kills as good as skinny feels."