Meprobamate

Meprobamate, sold under the brand names Miltown, Equalnil, Meproban, Procalmidol, Sedanyl, and more than 100 others (ref.) is a widely-used drug used to treat anxiety (i.e. an anxiolytic). Its chemical formula is C₉H₁₈N₂O_{4 ,}

It was first synthesized in the 1950s, and has been described as "the first blockbuster psychotropic drug in American history" ( ref.) earning 100s of millions of dollars for its (various) manufacturers.

It's known that meprobamate has barbiturate-like modulating actions on GABA_A receptors, leading to sedation and altered perception of pain - but the exact mechanism of action (which is believed to operate at multiple receptor sites in the nervous system ) is lacking a complete description.