Definitely xanax and heroin.. Kidding, but in all seriousness, like others have said Flexeril is great for getting drowsy (no more than 20mg) and Advil PM works great for me, better than Tylenol PM, oddly enough.
So you're way after acute dosing, right? Direct interactions should not be an issue, though the effects of JWHs on inflammation are unknown (possibly beneficial), depending on what you're treating using that prednisone.
The reply suggesting GHB gives an inordinately bad suggestion, due to addiction issues, dopamine rebound (or something else) limiting many to ~4 hrs. of g-sleep, and possible neurotoxicity depending on dosage.
Do you have any proof of GHB causing neurotoxicity? I have used Pure Pharmaceutical GHB for a number of years and have never heard of such an absurd statement like this.