Tetrovaline

Tetrovaline was a type of drug used in medicine to render certain types of lifeforms, including mammalian humanoids, into unconsciousness, with a side effect of lowered immune system response.

History and specific
Tetrovaline was among the medical supplies carried aboard the Delta Flyer. In the year 2376, Crewman Telfer asked to be knocked out with tetrovaline when he had a dark matter lifeform infiltrating his body, but Captain Kathryn Janeway wanted to keep his immune system response up and refused to use tetrovaline.