[malandrew]

Not exactly. Only one form of methamphetamine is psychologically active, the dextrotatory enantiomer. It's different from dextroamphetamine in that it contains a methyl group that makes it more lipid-soluble, which helps it cross the blood-brain barrier more easily and protects it from being broken down by MAO enzymes.

Dexedrine is the brand name for dextroamphetamine, the dextrorotatory stereo-isomer of amphetamine.

About 75% of Adderall is dextroamphetamine. The other 25% is composed of three other amphetamine salts.

The main reason methampetamine is smokeable is because it is sold on the street in fairly racemic crystal form (i.e. it contains both the active dextrotatory and levorotatory forms). If adderall, dexedrine and other prescription amphetamine salts were sold in the same form, free of the inert binders, they'd be smokeable too.