Metronidazole
"Went to the dentist June 14th, with Toothache, had some x rays taken, and saw there was an abscess on one of my upper right teeth. Prescribed me with 200mg, 3 per day of metronidazole which I have had before.  By the Thursday evening the right side of my face was swollen,  and Excruciating pain. Friday was no better. Today, (Saturday) swelling and pain had subsided a lot, but still there, especially in the jaw at the bottom. Hoping that by Monday, last day of taking them the abscess would have gone completely.  Back to the dentist in 3 wks time either to have root canal or have the tooth extracted."