ACE inhibitors are taken by thousands of patients and have been shown to be very safe. However, all medications have side effects, and there are some for which patients should be monitored. Because ACE inhibitors can lower blood pressure, lightheadedness and dizziness may result if blood pressure becomes too low. As ACE inhibitors reduce blood pressure only modestly in most patients, this is not a major problem, particularly if the initial dose is low. Oddly enough, the major side effect of ACE inhibitors is a cough. The cough occurs in about 15% of patients; however, it is mild in half of these patients and does not require stoppage of the drug. About 8% of patients have a cough bothersome enough that ACE inhibitor therapy has to be discontinued. Finally, ACE inhibitors can worsen kidney function in some patients, particularly if cholesterol buildup is blocking the arteries to both kidneys. However, long-term therapy with ACE inhibitors has been shown to prevent worsening of kidney function in patients with mild kidney disease due to diabetes or high blood pressure. If your gram-pa have abnormal kidney function, ask his doctor for more information.