Mefloquine is a chiral molecule with two asymmetric carbon centres, which means it has four different stereoisomers . The drug is currently manufactured and sold as a racemate of the ( R , S )- and ( S , R )-enantiomers by Hoffman-LaRoche , a Swiss pharmaceutical company. Essentially, it is two drugs in one. Plasma concentrations of the (–)-enantiomer are significantly higher than those for the (+)-enantiomer, and the pharmacokinetics between the two enantiomers are significantly different. The (+)-enantiomer has a shorter half-life than the (–)-enantiomer. 
Attention deficit hyperactivity disorder, better known as ADHD, is a controversial diagnosis marked by distractibility, hyperactivity, and impulsivity. Adults are more likely to be diagnosed with attention deficit disorder, or ADD, which lacks this hyperactivity characteristic, but is similar in other ways to ADHD. More than one in 10 children in the . will be diagnosed with ADD/ADHD, a figure that has grown exponentially in the last 50 years. Since 1957, doctors have been treating ADD/ADHD patients with psychostimulants like Adderall, Ritalin, and Concerta.