Methamphetamine is prescribed in the US for ADHD, under the brand name Desoxyn, and has a similar pharmacological profile to dextroamphetamine, but with fewer side-effects. Only differences are that people being prescribed it take pharmaceutical grade, rather than bob's-bathtub grade, take a dose 10-100 times lower and generally take it orally rather than inhaled or injected. Used appropriately, it's a very effective and safe drug. It's very rarely prescribed though, due to the stigma attached to it.