I'm quite certain that in Qnexa, the topiramate dose is released in the evening in order to reduce discomfort of the parasthesias side effect (the phentermine is immediate-release).
The question is whether this controlled-release feature is medically consequential. My contention is that it’s not and it was added to the product for marketing rather than medical reasons.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”