Hi there! As far as I'm aware, there's no footage of Neely losing consciousness (at least that's been released to the public), so we can't say how long Penny held onto the choke after Neely passed out. But I'll point out that three minutes is more than long enough to kill somebody.

A properly applied chokehold will knock somebody out in around 10 seconds (here's a video). And it works that fast because there's no blood getting to the brain anymore. Nothing to do with drugs.