The most common side effects with Irbesartan Hydrochlorothiazide Winthrop (seen in between 1 and 10 patients in 100) are dizziness, nausea (feeling sick) or vomiting, abnormal urination, fatigue (tiredness), and increases in blood urea nitrogen( BUN, a breakdown product of protein), creatinine (a breakdown product of muscle) and creatine kinase (an enzyme found in muscles).