Thenylfentanyl
Thenylfentanyl is an List of [fentanyl analogues|analogue] of fentanyl where the phenethylamine side-chain has been replaced by a thiophenylmethyl group. It was temporarily scheduled by the Drug Enforcement Administration in 1985, due to fears it would be used as a designer drug. But in 2010 the DEA acknowledged it was essentially inactive. Subsequently, the substance was since deregulated.