Nexium and Prilosec are heartburn medications — more specifically Proton Pump Inhibitors (PPI) — manufactured by AstraZeneca Pharmaceuticals. Nexium, whose active ingredient is Esomeprazole, is prescription medicine that is principally used to treat GERD and Zollinger-Ellison Syndrome. Prilosec, in which Omeprazole is the active ingredient, is available over the counter and less expensive than Nexium. Both drugs may be used in children, but only Nexium is approved for infants.

Comparison chart

Nexium versus Prilosec comparison chart
Edit this comparison chartNexiumPrilosec
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Active Ingredient Esomeprazole Omeprazole.
Conditions treated GERD, Zollinger-Ellison Syndrome, ulcers, heartburn. Duodenal ulcers, stomach ulcers, GERD, and erosive esophagitis, intially Zollinger-Ellison Syndrome.
Drug Type PPI (Protein Pump Inhibitor) Proton Pump Inhibitors (PPI).
Prescription Prescription required Over-the-counter or prescription.
Generic Version Unavailable Available.
Side Effects Headache, diarrhea, nausea, risk of bone fractures, stomach lining inflammation Headache, diarrhea, nausea, risk of bone fractures, stomach lining inflammation.
Dose As prescribed 2 times daily for 10 days; once a day for 18 days if ulcer is present.
Pregnancy Category B (USA): Safe during pregnancy C (USA): Not safe during pregnancy, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
Delayed reslease Yes Yes.

What are Proton Pump Inhibitors?

Heartburn can be treated in three different ways: with Antacids, H2 blockers and Proton Pump Inhibitors (PPI). The stomach has tiny pumps which produce acid to break down ingested food. If the acid is produced in excess and refluxes into the esophagus, it causes heartburn. Proton pump inhibitors turn off pumps in the stomach to reduce acid production to an amount just enough for digestion. While Antacids and H2 blockers provide temporary relief for a few hours, proton pump inhibitors like Nexium and Prilosec can provide relief for a longer duration.

This video explains how PPIs work:

Active Ingredients

The active ingredient in Nexium is Esomeprazole, an S-enantiomer of Omeprazole, the active ingredient in Prilosec.

Esomeprazole is used primarily for gastroesophageal reflux disease, treatment and maintenance of erosive esophagitis, treatment of duodenal ulcers caused by H. pylori, prevention of gastric ulcers in those on chronic NSAID therapy, and treatment of gastrointestinal ulcers associated with Crohn's disease. Omeprazole is used to treat gastroesophageal reflux disease, gastric and duodenal ulceration, and gastritis.

People with allergies to Esmeprazole should avoid Nexium, and those with allergies to Omeprazole should not take Prilosec.


Nexium and Prilosec are used to reduce the acid in the stomach that causes frequent heartburn and conditions associated with it.

Nexium is mainly used as a treatment for GERD (Gastro esophageal reflux disease) and Zollinger-Ellison Syndrome, which produces tumors that secrete excess stomach acid. Nexium can also be used to treat duodenal ulcers, stomach ulcers, and stress-induced ulcers.

Prilosec, in conjunction with other medications, can be used to treat or prevent duodenal ulcers, stomach ulcers, GERD, and erosive esophagitis. It can also be given in the initial stages to patients with Zollinger-Ellison syndrome. Both drugs can be used to treat NSAID-induced ulcers. (NSAID is a class of anti-inflammatory drugs containing, acetaminophen, ibuprofen or aspirin, among others.)

Prilosec can be used for both adults and children, while Nexium is only prescribed for adult patients.


In a study conducted by NIH, esomeprazole (Nexium) was seen to be more beneficial and safer for patients with gastroesophageal reflux disease (GERD). Esomeprazole was superior to omeprazole for all secondary measures and had a similar safety profile.

40 mg esomeprazole was also seen as more effective controlling acid in GERD patients than twice the dose of omeprazole (Prilosec).

Side Effects

Common Side Effects

Both Nexium and Prilosec have similar side effects. Common side effects include headache, diarrhea, nausea, gas, abdominal pain. In addition, Nexium can cause constipation, dry mouth, and drowsiness; Prilosec can cause vomiting.

In children, Nexium can cause headache, diarrhea, abdominal pain, nausea. Prilosec, in addition to the side effects above, can also cause respiratory problems and fever.

Prilosec is not recommended for infants. Nexium can be prescribed to infants ages 1 month to 1 year, but can cause side effects of abdominal pain, regurgitation and rapid heartbeat.

Serious Side Effects

With long term use, both drugs can cause risk of bone fractures, inflammation of the stomach lining and lower magnesium levels in the body. In addition to these, both can cause seizures, dizziness, cramps, spasm of the voice box, muscle weakness, jitters, and rapid heartbeat.

Health expert and radio talk show host Dr. Tom Roselle speaks on the dangers of proton pump inhibotors like Nexium and Prilosec:

Availability and Cost

Nexium is a prescription drug with no generic equivalent available. Prilosec costs much less, and since it does not require prescription, it can be bought over the counter even in generic form (omeprazole).


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