Is this a normal reaction?

about 6 hours ago I was experiencing debilitating female cramps while in an important meeting. I was unable to get up and leave the room, so my co-worker slipped me a couple of her 800mg muscle relaxers. I took one and after about 20 minutes was still in serious pain, so I took half of another one. This was around 1pm. I would say it took until around 2 or 3 pm for the pain to completely subside, although she said they usually only take about 20 min. to work. Either way, I felt better, and after the meeting did some errands and had a bite to eat at home. Around 4pm I was doing some work on my laptop and suddenly became exhausted. I could not keep my eyes open anymore and laid down on the couch for a bit. Now it is 7pm. At 6:15 it was a real struggle to wake up, and I still feel extremely groggy and a bit nauseous. It just seems like a very long time frame for the drugs to take hold in. Is this normal with muscle relaxers or could I be coming down with something? I wouldn't think they would still be effecting me this hard.