Hydrochlorothiazide
"I was taking Micardis/hctz for about 8 years(HCTz is hydrochlorthiazide)  I began having abdomen pain, bloating and diarrhea.  I went to my PCP.  He did a bunch of blood tests and referred me to a GI specialist.  I had an EGD which is a scope of my stomach and a colonoscopy.  All tests were negative.  I continued to have these side effects.  After much searching on various websites I discovered that HCTZ should not be given to people with an allergy to penicillin.  I went to my PCP and asked to be taken off the combination drug and to take only telmisartin which is the other drug in Micardis.  Within 24 hours my symptoms were gone."