Phentermine is an amphetamine-derived drug; topiramate is an anti-convulsant. t yet submitted their drug for Health Canada approval, according to a spokesperson. Past attempts to bring — and keep —. Later this week, an advisory panel to the agency is set to review Qnexa, a weight-loss drug developed by Vivus Inc. The drug combines phentermine, an appetite suppressant, with topiramate, an epilepsy. Discussion Forums NEW! Discussion Forums Recent Forum Topics…