How effective and safe are pepto-bismol and tums (calcium carbonate)? how do they work?

Fairly safe: Both are reasonably safe for short term use. However, long term use can lead to problems. Both work primarily by coating the stomach to help acid effects. With prolonged use the normal bacteria in the GI tract can be depleted and abnormal bacteria can overgrow. Alos prolonged use of peptobismol can cause discoloration of the intestinal tract along with elevated levels of bismuth.

Instructions: Follow instructions for these products. Tums contain calcium and too much is dangerous. They provide only temporary relief of heartburn by neutralizing stomach acid. Pepto bismol contains bismuth which reduces diarrhea. It may turn your BM's blackish but has little other side effects. Follow directions!