There is no way to compare which one has more side effects between Famotidine and Omeprazole, side effects vary from person to person. Famotidine side effects include dry mouth, dizziness, etc. Omeprazole side effects include diarrhea. 1. Famotidine is indicated for peptic ulcer, reflux esophagitis and other diseases. Side effects include dry mouth, dizziness, constipation, diarrhea, rash, leukopenia, increased blood pressure, facial flushing, jaundice liver function abnormalities, depressive state, convulsions, etc. Prohibited in patients with severe renal insufficiency. 2. Omeprazole is suitable for duodenal ulcer, stress ulcer and other diseases. Adverse reactions include diarrhea, nausea, abdominal pain, constipation, rash, drowsiness, angina pectoris, tachycardia, peripheral edema, hepatic necrosis, hepatic encephalopathy and so on. Contraindicated in patients with bronchospasm. If you need to use the above medications, it is recommended to consult a doctor and take the medication as prescribed.