Verilamine

Verilamine was a type of truth drug. It compels the subject to answer questions.

History and specifics
In 2273, disgraced physician Anton Zauber assumed the identity and appearance of Leonard McCoy as part of a conspiracy to steal royalties from his patents. After McCoy had been injected with a paralysis drug, Zauber stole his clothes and wrist communicator. To get information he'd need to maintain his impersonation of McCoy aboard the USS Enterprise (NCC-1701), Zauber injected McCoy with five grains of verilamine. The dosage enabled McCoy to speak and answer truthfully, without otherwise affecting his paralysis.