One type of anti-diarrheal drug that can cause potential side effects such as dry mouth, tachycardia, abdominal pain, and blurred vision is loperamide. Loperamide is a medication that works by slowing down the movement of the intestine and increasing the absorption of water and electrolytes, which helps to reduce diarrhea. While loperamide is generally well-tolerated and effective at treating diarrhea, it can cause side effects in some people. Dry mouth, tachycardia, abdominal pain, and blurred vision are all potential side effects of loperamide, although they are relatively rare. Other potential side effects of loperamide may include constipation, dizziness, and nausea. It is important for patients to be aware of the potential side effects of loperamide and to report any unusual symptoms to their healthcare provider.