This will be a randomized, double-blind, placebo-controlled, parallel group, safety and tolerability study in adults with ADHD. The target subjects are healthy male or female adults aged 18 to 64 years, inclusive, with a diagnosis of ADHD. A total of fifty subjects will be enrolled at approximately 5 sites in the US. Subjects will be randomized (1:1) to one of two treatment groups, SPN-812V or placebo.