(slang) (Legal or illegal medicinal) tranquilizers (for human consumption).
1975, Russell H. Greenan, Heart of Gold, page 114:
"If the girl wants to sleep, let her do it on her own time. She must have gulped a handful of tranx, for Christ's sake. I couldn't even get her to make conversation."
"Hey, man—now listen. Greta wouldn't take no tranx when she's working."
1988, New Society, page 134:
No tranx
Minor tranquillisers are among the world's most commonly prescribed drugs.