Omeprazole, which is classified as a proton pump inhibitor is used to decrease the production of acid in the stomach. Omeprazole prevents the activities of stomach enzymes that produce stomach acid. Long-term suppression of stomach acid by omeprazole may cause side effects.
Long-term use of omeprazole may cause pancreatitis, according to Drugs.com. Pancreatitis is the inflammation of the pancreas, an organ that produces digestive enzymes important for the digestion of fats and carbohydrates. The pancreas also produces insulin, a hormone important in the control of blood glucose levels. Signs and symptoms of pancreatitis include nausea and vomiting, fever, chills, pain in the upper abdomen, fatty stool, rapid heart rate, sweating and rapid breathing.
Chronic use of omeprazole may cause interstitial neprhritis, inflammation of the spaces between kidney tubules. Interstitial nephritis reduces the kidneys' ability to remove waste products from the body and may eventually lead to kidney failure. Signs and symptoms of interstitial nephritis include decreased urination, sudden weight gain, confusion and changes in mental status, blood in urine, nausea and vomiting.
The U.S. Food and Drug Administration warns that long-term use of high doses of omeprazole and other proton pump inhibitors may lead to increased risk of fractures of the hip, spine and wrists. Patients with bone problems such as osteoporosis should avoid omeprazole. The FDA advises consumers not to take more than three 14-day courses of omeprazole in one year.