Neurocine

Neurocine is a chemical that is typically delivered in gaseous form as an anesthetic. High concentrations of neurocine can be fatal

The Cardassians used lethal concentrations of neurocine as crowd control and as part of a counter-insurgency program aboard. 

Neurocine was also used to incapacitate Romulan hijackers aboard the USS Prometheus in 2374. as well as allow the to steal a Jem'Hadar attack ship and its Breen weapon in 2375. 

In 2377, Dr. Alan Murrow assisted the USS Baldwin (NCC-2013) crew in destroying a Jem'Hadar dreadnought by flooding the ship with neurocine.