Metraprovoline is a drug.
Metraprovoline can be used to simulate the hormonal and biochemical profile of a Trill individual in the body of a non-Trill individual who has been joined with a symbiont. (ST - Divided We Fall comic: "All Fall Down", ST reference: The Starfleet Survival Guide)
In 2376, Julian Bashir used metraprovoline, lethozine and metrazene when Ezri Dax started to reject the Dax symbiont after an encounter with the "cathedral artifact" in the Gamma Quadrant. (DS9 - Mission Gamma novel: Cathedral)