Saw this movie on HBO/Cinemax probably around 1995. These seedy underground types were taking drugs but over time they were transforming them into monsters or something?? I’m pretty sure I watched the immortals with Tia carrerre that same weekend bc I was a kid and visiting my aunts house who actually had uncensored TV.
Underworld (1985)?
Full Eclipse (1993) starring Mario Van Peebles. I think it was a made for HBO movie.
That was my first thought, too. But the cops were the werewolves in Full Eclipse. It doesn’t quite fit the OP’s description.