In my opinion, it is safe. I've taken over a dozen fioricet and up to 300 mg (30 × 10 mg tablets) zolpidem (ambien) within a 24 hour interval of time. While I'm not advocating or advising such heavy drug use as that, I'm merely using my experiences to put your own use into a proper perspective. That is to say, if 12+ fioricets followed by 30 ambien didn't kill or maim or injure me, I'd find it unlikely for a paltry 4 fioricets and 1 ambien to kill you.