Usually used by people looking to trade sex for pills.
Also commonly used with the term Molly, as in the pure form of MDMA, or better known as Ecstasy.
A classic example came from a Craigslist post:
Looking for my friend Molly and her Viking friends. We like to hang out in the afternoon, about 40 mins before 5 o'clock. Since I like to party so much I'd like to know who else can come along. Respond and we can go from there.
Guy 1: "Hey man, let's go talk to those chicks over there."
Guy 2: "No way man, my girl would get pissed at me if she saw me talking to them."
Guy 1: "Dude, your woman isn't even here! C'mon."
Guy 2: "Doesn't matter man, somehow, she would just know."
Guy 1: "Man, you are such a douchenozzle."