Dexedrine (n.)

word-forming element meaning "toward or on the right-hand side," from combining form of Latin dexter (from PIE root *deks- "right, opposite of left; south").

trade name of a type of amphetamine, 1933, registered as a proprietary name 1935 by Smith, Kline & French Laboratories, from benzoic (see benzene) + chemical suffix -edrine from ephedrine, etc. It is a carbonate of benzyl-methyl-carbinamine. Slang shortening benny is attested by 1955.