Metronidazole
"I was diagnosed with a mild case of diverticulitis.  I had severe abdominal pain mainly on left side, low grade fever and headache.  I was prescribed Flagyl every 6 hours for 10 days and bactrim every 12 hours for 10 days.   Ugh... 60 pills.....  I felt much better abdominal wise after 2 days but the side effects were horrible! Sour stomach and headaches..  After day 4 I decided to do some research.  I learned that you should space these meds at least an hour apart.  (helped a ton).  You should also eat a piece of bread with or have something on your stomach when you take them.  Drink as much water as you can and take prebiotics and probiotics to help your stomach stay balanced.  I was also recommended taking  a Leaky Gut Repair health supplement"