VVUS
>>Qnexa (Q-NEX-uh) is a once-a-day, proprietary, oral, controlled-release formulation of low dose phentermine and topiramate.<<
Typical formulators of the 2 generics might not duplicate the controlled-release feature described above. I have no current idea whether that is a feature of the claims of any patent VVUS may have, or whether controlled-release is critical to the purported safety[and efficacy] of the product.