Both Nexium and Prilosec belong to the class of medicines called proton pump inhibitors (PPIs). Even though there are many similarities between them, there are several differences, such as:

• Nexium is a brand name for esomeprazole and Prilosec is a brand name for omeprazole
• Omeprazole is a mixture of two stereo-isomers: R-omeprazole and S-omeprazole. Stereo-isomers are compounds that have the same chemical formula but differ only in their arrangement of atoms. Esomeprazole contains only one isomer, S- omeprazole. This means that Prilosec contains two isomers of omeprazole, while Nexium only contains one
• There is some evidence that Nexium provides more effective acid control, lasts for longer, and works faster than Prilosec; however, some studies have failed to find a difference between the two medicines and the American College of Gastroenterology states that there are no major differences between PPIs when used to treat GERD
• Nexium is typically more expensive than Prilosec; however, generic versions have similar prices
• Although side effects (such as diarrhea, nausea, vomiting or headache) with PPIs are uncommon, Nexium may be more likely than Prilosec to cause them
• Prilosec should not be taken with the blood thinner clopidogrel. It is unclear whether Nexium has a similar interaction with clopidogrel as it has not been evaluated.

Because both medicines are PPIs, there are a number of similarities, such as:

• Both Nexium and Prilosec work by irreversibly blocking the actions of an enzyme responsible for acid production, called H+/K+ ATPase (also known as the gastric proton pump). This is located in certain cells in the stomach wall. Both baseline gastric acid secretion and stimulated gastric acid secretion (in response to food) are affected. This allows damaged tissue in the esophagus, stomach, and duodenum to heal
• Both are available as over-the-counter medicines, without a prescription
• Generics are available under the name esomeprazole (Nexium) and omeprazole (Prilosec)
• Both Nexium and Prilosec may be used to treat symptoms of gastroesophageal reflux disease (GERD), conditions involving excessive stomach acid such as Zollinger-Ellison syndrome, esophagitis (an inflammation or erosion of the esophagus), stomach and duodenal ulcers (either caused by Helicobacter pylori infection or nonsteroidal anti-inflammatory drugs [NSAIDs])
• Long-term use of Nexium and Prilosec may increase the risk of osteoporosis-related fractures of the hip, wrist, or spine; Clostridium difficile-associated diarrhea; pneumonia; or low vitamin B-12 and magnesium levels
• Neither Nexium or Prilosec will offer immediate relief from heartburn. Antacids are used for this purpose
• Neither Nexium or Prilosec should be used for longer than four to eight weeks, unless a doctor determines otherwise
• Both Nexium and Prilosec may interact with other medications, such as HIV medications (such as delavirdine, nelfinavir, rilpivirine), rifampin, risedronate, St. John’s wort, and several other medications. Nexium or Prilosec may also interact with methotrexate or reduce the absorption of drugs that are dependent on a low gastric pH for their absorption.