Clindamycin
"All I can say is I had two teeth pulled 6 days ago, by the 2nd day I had a horrible taste in my mouth, a constant headache, and pain in my gums while on pain killers. I went to the ER and the Dr prescribed 300 mg every 6 hours. So 4 days now on the medicine and pain killers and my gums still hurts and I still have a headache?  I have been prescribed this medicine in the past and it normally works with no side effects. I have no idea why am I still in pain, while the pain killers do not make it go away, it makes the pain tolerable so I can do my every day things."