Hello, I Was Experiencing Some Really Bad Premenstrual Cramps This

hello, I was experiencing some really bad premenstrual cramps this a few hours ago today. I took 600mg ibuprofen and although the sharp pains went a way with in 10 minues and I felt much better. Now I am really sleepy and almost drowsy and dizzy. I did take the medication on an empty stomach. But I had a pretty big lunch about an hour later. Now it's been about 2.5 hours since I tool the ibuprofen and I'm really sleepy and tired. But I'm at work so obviously I can't lie down or take a nap or anything. Is this a normal side effect?