Metronidazole
"Second time taking this anabiotic, first time it wasn't bad at all. No symptoms for me. This time on the 4th or 5th day I woke with a headache then the nausea on top of all that I can't sleep at night I'm usually knocked out around 10ish for work in wide awake, like no sleep is in my future lol don't mean to laugh but gotta cheer up some how. I also have no appetite, & it's not because of the nausea. Not sure what's different this time, but I don't ever want to go through this again, restless nights so tired & can't sleep. Not cool at all!! But I found a remedy take some Pepto-Bismol it coats your stomach & will help with the  nauseous feeling a lot. It helped me & I had to make myself eat even though I had no  appetite Hope this was some help"