Crossword clues for the word: TRUTHSERUM The word TRUTHSERUM has appeared as an answer to at least 8 crossword clues on different crossword puzzles. Crossword clues for TRUTHSERUM Showing 1 to 8 of 8 results Clue(s) Helpful dosage for Feb. 22. Injection in some spy movies People can't lie under it Psychotherapy aid Scopolamine Sodium pentothal Straight shot? Substance on which it's hard to lie?