This three-arm, parallel group, double-blind, active- and placebo-controlled study comparing VI-0521 at a potential therapeutic dose of PHEN/TPM 7.5/46 and PHEN/TPM 22.5/138 , a supra-therapeutic dose, with placebo. A single oral dose of 400 mg moxifloxacin is included as a positive control in terms of the effect on cardiac repolarization. The three treatment regimens are defined as follows: