[thirtyseven]

Yes you can. Methamphetamine is used to treat ADHD under the trade name of Desoxyn.

http://www.webmd.com/drugs/2/drug-9124/desoxyn-oral/details

[DaiPlusPlus]

Yes, but you can't simply "buy it" from Target.

[mcbits]

You can buy it in the same sense that you can simply buy cigarettes. Just the documentation requirements are different.