This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
Isoboramine (also spelled as isoboromine) was a neurotransmitter in Trill symbiont physiology which regulated the connections between the host and the symbiont. Low isoboramine levels were harmful and could be fatal to the host and/or symbiont, so if isoboramine levels dropped below 40%, the symbiont was typically removed, killing the host to save the symbiont.
Benzocyatizine was administered to treat low isoboramine levels.
Official records at the Trill Symbiosis Commission stated that in 2285, when Torias Dax was in a shuttle accident, he was placed in a coma. He was left in a vegetative state until his isoboramine levels eventually fell below 40% and the symbiont had to be removed. In actuality, the symbiont had been transferred to Joran Belar.