Metronidazole
"Insomnia was the only really troubling side effect for me. Slight metallic taste in mouth around day 3, but was gone in 24 hrs. Mild diarrhea, stomach was a bit more acidic than usual but nothing I couldn't deal with. Always took with full meal, had NO ALCOHOL (even mouthwash with alcohol is too much on this med re: pharmacist) and took with Gatorade (helps with bad taste). Be gentle with your body on this med. I found that not having caffeine, any NSAIDs (ibuprofen, aspirin, naproxen, etc.) or anything harsh on the stomach works best. DO NOT DRINK ALCOHOL while on this med - EVEN 1 DRINK. I had already tried 1 course of penicillin and 1 course of amoxicillin before this med, neither worked - 6 days on this, jaw pain & swelling is gone!"