Generic Prilosec: uses, doses, and side effects

If you get frequent heartburn or live with a chronic condition like GERD (gastroesophageal reflux disease), you know that everyday antacids don’t always cut it.

To treat chronic heartburn, your healthcare provider may recommend over-the-counter (OTC) or prescription medication, which includes proton pump inhibitors (PPIs) like Prilosec or H2 antagonists like Zantac—one of the first drugs developed to treat peptic ulcers (Nugent, 2020).

Prilosec and its generic version, omeprazole, are PPIs, effective for the treatment of certain gastrointestinal conditions, and are available both over-the-counter (OTC) or with a prescription. Here’s what you need to know about Prilosec, what it’s used for, its potential side effects, and how it compares to the generic alternative.  

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Prilosec, known in its generic form as omeprazole, is a drug commonly used to treat chronic digestive conditions like GERD. While the prevalence of GERD varies, studies show that roughly 23% of adults in North America live with this condition (El-Serag, 2014). Prilosec was originally only available as a prescription medication until the U.S. Food and Drug Administration (FDA) approved an OTC version in 2015 (FDA, 2015). 

Prilosec comes in delayed-release capsules or is available as an oral suspension that you can mix into applesauce for those with trouble swallowing pills. Recommended dosages are 10 mg, 20 mg, 40 mg, and 60 mg, depending on what condition you’re using it for (FDA, 2018). Your age and weight may also factor into your dosage. Although Prilosec starts working right away, it can take up to four days before you feel the full effects. Do not take Prilosec OTC for more than 14 days in a row without consulting a healthcare provider (Prilosec, 2019). 

Like other PPIs, Prilosec helps treat conditions caused by high stomach acid levels. Studies have also found it plays a preventative role in patients at risk of upper gastrointestinal tract bleeding or those who take medications that may increase their risk of upper GI bleeds, such as nonsteroidal anti-inflammatory drugs (NSAIDs) (Khan, 2018). Here are the main uses of Prilosec (NLM, 2019): 

GERD

While almost everyone experiences occasional heartburn, if it occurs more frequently, it may be a sign of GERD, a digestive disease that causes irritation and inflammation of the esophagus (the tube that leads from your mouth to your stomach) due to acid coming up out of your stomach. Symptoms vary, but people with GERD often experience recurring heartburn, regurgitation, difficulty swallowing, burping, cough, or a bad taste in the mouth (Sandhu, 2017). PPIs such as Prilosec are an effective treatment for GERD and work by reducing the amount of acid in the stomach. 

Esophagitis

Conditions like GERD can lead to esophagitis, which is when the esophagus becomes irritated or inflamed due to frequent acid reflux. Symptoms of esophagitis can include heartburn, regurgitation, and difficulty swallowing. Left untreated, it can cause permanent damage to the esophagus. A potentially precancerous condition called Barrett’s esophagus can also develop, which is when the lining in the esophagus turns into tissue similar to that of the stomach (Wang, 2015). With proper treatment, these changes are reversible. But if left undiagnosed, Barrett’s esophagus can cause serious medical problems. 

Duodenal and gastric ulcers

Peptic ulcers — lesions that develop in the stomach or small intestine from damage to the lining in these organs — are also treated with PPIs, which help provide relief from symptoms and help ulcers heal. A number of things can cause peptic ulcers to develop, but the most common culprits are Helicobacter pylori infections in the stomach and the frequent use of NSAIDs (like aspirin, Advil, or Motrin) (ACG, 2012). 

Zollinger-Ellison syndrome 

Zollinger-Ellison syndrome is a very rare condition that results in the release of excessive gastrin, a hormone that stimulates acid secretion in the stomach (NORD, n.d.). This acid can cause heartburn or the formation of ulcers in the stomach or small intestine. 

Both Prilosec and the generic version, omeprazole, which we’ll delve into more below, are relatively inexpensive as far as drugs go, though prices may vary depending on whether or not you have health insurance and which kind you have.

Omeprazole is the generic form of Prilosec and is just as effective as the brand name product. Another brand name version of omeprazole is Losec. Omeprazole works by blocking proton pumps (specialized mechanisms in the body that produce stomach acid), thereby reducing acid levels in the stomach (FDA, 2018).

Aside from omeprazole, there are other types of PPIs — like pantoprazole and lansoprazole, for example — that work the same way. Most of these medications are deemed both safe and effective (IFFGD, 2020).  

The side effects of Prilosec vary, with the most common symptoms, including headaches, dizziness, nausea, diarrhea, rash, cough, and constipation. Less common side effects include loss of appetite, hair loss, and changes in taste (Casciaro, 2019).

Prilosec may also trigger less common side effects related to underlying health conditions, such as bone fractures and chronic stomach inflammation. Serious side effects are rare but may include pancreatitis, kidney inflammation, and liver damage (FDA, 2018). 

Prilosec is safe for many people to take. However, certain people may require a lower dose, and some should avoid the drug entirely. 

Solid scientific research on the effects of omeprazole in pregnant women is lacking, making it difficult to predict any adverse effects or risk to the fetus (FDA, 2018). No negative impacts have been reported so far for nursing mothers, although there is evidence that omeprazole gets into breastmilk (NLM, 2019). 

Prilosec can be taken by children under the guidance of a healthcare professional, although there isn’t enough research yet to determine if it’s safe for infants (FDA, 2018). Consult a pediatrician before giving this medication to a child.  

Even if you’re only taking OTC Prilosec, it’s important to speak with your healthcare provider first. Also, keep in mind this drug is intended to treat frequent heartburn—not to immediately relieve symptoms or for occasional heartburn (FDA, 2015). 

If you have an allergy (or suspect you might) to medications similar to omeprazole, or if you take certain antiretroviral drugs (medications that help treat HIV), do not use this drug (NLM, 2019).  

Prilosec can interact with many other medications. Some interactions may be mild, but some can be severe. Here are some of the most important drugs to be aware of while taking omeprazole (FDA, 2018):

• Antiretrovirals: Prilosec may cause certain antiretrovirals, which are used to manage HIV, to become less effective. Examples of these drugs include rilpivirine, atazanavir, nelfinavir, and saquinavir.

• Warfarin: Warfarin is an anticoagulant that prevents blood clots from forming. When combined with warfarin, omeprazole can increase the risk of bleeding. 

• Methotrexate: A therapeutic drug used to treat arthritis and certain cancers, combining omeprazole with methotrexate can result in toxic levels of methotrexate in the blood.

• Clopidogrel: Taking blood thinners such as clopidogrel with Prilosec could decrease its effectiveness and increase a person’s chance of developing a blood clot. This is because of the effect that the liver has on this medication. Other drugs similarly affected by omeprazole include citalopram, cilostazol, phenytoin, diazepam, and a heart medication known as digoxin.

• Tacrolimus: Tacrolimus is a medication used to prevent organ rejection after a transplant. PPIs like Prilosec may increase levels of tacrolimus in the body.

This doesn’t include all the potential drug interactions with Prilosec. Consult with your healthcare provider first before taking PPIs, especially if you have underlying health conditions or are taking any other medication. For more on side effects, safety, and prescribing information, read the FDA-approved Prilosec prescribing information.

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Current version

October 16, 2020

Written by

Anna Brooks

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.