Proton pump inhibitors (PPIs) like omeprazole and lansoprazole remove acid from the stomach. Omeprazole side effects are unusual although, like all drugs, there is a long list of things which can trouble people.
The list below is not complete but gives a general guide to some of the side effects that are seen with these drugs.
Common side effects which occur in more than 1% of people who take these medicines are usually mild and include:
Risks of Removing Acid from the Stomach
People are often concerned that removing acid from the stomach may cause damage. It is worth remembering that the medicine works for around 12 hours so if taken once a day, the stomach will in fact be acidic for half the day.
Nonetheless, there are some definite small risks associated with taking these drugs long term.
Clostridium difficile diarrhoea is a rare cause of severe diarrhoea. It is frequently contracted in hospitals. Taking a PPI can double the risk (1).
Pneumonia (chest infections) are also more common in people taking PPIs. (2)
Hip fractures may be more common in people taking PPIs for a long time. The evidence for this is just starting to emerge and it is not yet clear how big, if any, this effect is. (3, 4). Interestingly, one of the sources of this information, the UK General Practice Research database, was analysed a second time and the opposite conclusion was reached, that PPIs do NOT cause an excess in hip fractures. (4). This is definitely an area to keep watching as our understanding improves.
Hypomagnesaemia is a low magnesium level in the blood. This is occasionally seen in people who take proton pump inhibitors long term. It usually responds to stopping the drug.
Heart Rhythm Disturbances have been reported in a recent scientific paper. This is a new description. Time will tell how important or frequent this problem turns out to be. People who have heart rhythm problems should discuss this with their doctor. (5)
Rare side effects can be severe. These include:
Stopping Proton Pump Inhibitors
In 2009 a report in the prestigious journal, Gastroenterology suggested that PPIs may cause a degree of dependence by increasing symptoms of indigestion if they are discontinued. (6)
In 2010, the American Journal of Gastroenterology reported on healthy volunteers who were given pantoprazole or a dummy pill (placebo) for 4 weeks and then followed for another 6 weeks. One week after they stopped treatment, 44% of the people who had taken pantoprazole reported symptoms of dyspepsia, compared to 9% of the placebo recipients. By the third week, the difference had disappeared. (7)
This suggests that there is rebound excess acid production when the medicines are stopped. It is thought that more of the hormone gastrin is secreted PPIs are stopped and this leads to worsening acid symptoms for a week or two after stopping these drugs.
A case can therefore be made for decreasing the dose of these medicines slowly rather than suddenly discontinuing them. This might be a way to minimize omeprazole side effects and side effects from other proton pump inhibitors.