The generic name of Nexium is Omeprazole, and there are some differences between Omeprazole and Rabeprazole in terms of onset of action time, indications and adverse reactions. 1. Onset of action: Omeprazole is a first-generation proton pump inhibitor, which starts to take effect 1~2 hours after oral intake, while rabeprazole is a third-generation proton pump inhibitor, which starts to take effect 1 hour after the first dose. 2. Indications: Rabeprazole is usually used in the treatment of active ulcers, esophagitis and other diseases; omeprazole is mainly used for reflux esophagitis, peptic ulcer, upper gastrointestinal bleeding. 3. Adverse reactions: omeprazole more frequent adverse reactions are gastrointestinal reactions, such as nausea, vomiting, abdominal pain, etc., as well as headache and other neurological symptoms; rabeprazole’s occurrence of more adverse reactions in addition to gastrointestinal reactions and erythrocytopenia, urticaria and so on. Patients who need to use omeprazole or rabeprazole treatment should be under the guidance of a doctor.