Omeprazole side effects & cautions

Updated February 12, 2018

Omeprazole is in a category of drugs called proton pump inhibitors (PPIs). These block the production of stomach acid. Available by prescription and over the counter, omeprazole is sold in generic form and under the brand name Prilosec. Most people do not experience any side effects.

Most Common Effects

In clinical trials with omeprazole, as summarised by eMedTV, side effects occurred in between 1 per cent and 7 per cent of participants. These included abdominal pain, back pain, constipation or diarrhoea, upper respiratory tract infections and dizziness.

Less Common Effects

Less common omeprazole side effects include nausea, vomiting, leg cramps, muscle pain, nervousness, weakness and water retention.


Rarely, omeprazole can cause pancreatitis, with symptoms of nausea, fever and chills, significant upper abdominal pain, and a rapid heartbeat.

Hip Fracture Risk

According to a study published in the Journal of the American Medical Association (JAMA) in 2006, long-term therapy with PPIs, including omeprazole, is associated with an increased risk of hip fracture.

Allergic Reaction

Rarely, people experience an allergic reaction to omeprazole. Signs include rash or hives, difficulty breathing, and throat, face or mouth swelling.

Drug Interactions

Omeprazole interferes with various drugs, including diazepam, warfarin, phenytoin, ketoconazole, digoxin, saquinavir, nelfinavir and atazanavir.

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About the Author

Shelley Moore is a journalist and award-winning short-story writer. She specializes in writing about personal development, health, careers and personal finance. Moore has been published in "Family Circle" magazine and the "Milwaukee Sentinel" newspaper, along with numerous other national and regional magazines, daily and weekly newspapers and corporate publications. She has a Bachelor of Science in psychology.