I was once prescribed a drug called Edronax (Reboxetene). I could have erections just fine, but as an added bonus, I could come without them, too. Erections and orgasms seemed disconnected, somehow.
@bigjpgh: BTW, Former manager of The Doors, Danny Sugerman, describes exactly this as he was withdrawing from heroin in his book Wonderland Avenue. A chilling book about "altered states".