It is quite common for the combination of aspirin and clopidogrel (Plavix) to cause mild stomach irritation or changes in bowel habits, especially in the weeks following your angioplasty. While a medication like pantoprazole is very helpful for protecting your stomach lining, it can sometimes contribute to loose stools. Because staying on your prescribed blood thinners is absolutely vital for your heart's healing right now, please contact your doctor or cardiologist before making any changes.