Prilosec OTC Side Effects

Generic name: omeprazole

Medically reviewed by Drugs.com. Last updated on Feb 5, 2025.

Note: This document provides detailed information about Prilosec OTC Side Effects associated with omeprazole. Some dosage forms listed on this page may not apply specifically to the brand name Prilosec OTC.

Applies to omeprazole: oral capsule delayed release, oral packet, oral powder for suspension, oral tablet disintegrating delayed release, oral tablet delayed release.

Precautions

It is important that your doctor check your or your child's progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. Blood, urine, and other laboratory tests may be needed to check for unwanted effects. If your or your child's condition does not improve, or if it becomes worse, check with your doctor.

Tell your doctor if you have Asian relatives, such as Filipino, Chinese, Japanese, Korean, or Taiwanese. You may need a lower dose of this medicine to treat erosive esophagitis.

Do not use omeprazole (the active ingredient contained in Prilosec OTC) if you are also using medicines containing rilpivirine (Edurant®, Complera®). Using these medicines together may cause unwanted side effects.

This medicine is sometimes given together with other medicines to treat ulcers. Be sure you understand about the risks and proper use of any other medicine your doctor gives you or your child together with omeprazole.

Omeprazole may cause a serious type of allergic reaction when used in patients with conditions treated with antibiotics. Call your doctor right away if you or your child has itching, trouble breathing or swallowing, or any swelling of your hands, face, or mouth.

Check with your doctor right away if you or your child has a change in frequency of urination or amount of urine, blood in the urine, fever, joint pain, loss of appetite, skin rash, swelling of the body, feet, or ankles, unusual tiredness or weakness, or unusual weight gain after receiving this medicine. These could be symptoms of a serious kidney problem called acute tubulointerstitial nephritis.

Taking this medicine for a long time may make it harder for your body to absorb vitamin B12. Tell your doctor if you have concerns about vitamin B12 deficiency.

Serious stomach conditions may occur while taking this medicine alone or together with antibiotics. Check with your doctor immediately if you or your child has stomach cramps, bloated feeling, watery and severe diarrhea which may also be bloody sometimes, fever, nausea or vomiting, or unusual tiredness or weakness.

This medicine may increase your risk of having fractures of the hip, wrist, and spine. This is more likely if you are 50 years of age and older, if you receive high doses of this medicine, or use it for one year or more. Call your doctor right away if you have severe bone pain or are unable to walk or sit normally.

This medicine may cause serious skin reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalized exanthematous pustulosis, and drug reaction with eosinophilia and systemic symptoms (DRESS). Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, swollen glands, unusual bleeding or bruising, or unusual tiredness or weakness.

This medicine may cause hypomagnesemia (low magnesium in the blood). This is more likely to occur if you are taking this medicine for more than 1 year, or if you are taking this medicine together with digoxin (Lanoxin®) or certain diuretics or "water pills". Check with your doctor right away if you have convulsions (seizures), fast, racing, or uneven heartbeat, muscle spasms (tetany), tremors, or unusual tiredness or weakness.

Cutaneous or systemic lupus erythematosus may occur or get worse in patients receiving a PPI. Call your doctor right away if you have joint pain or a skin rash on your cheeks or arms that gets worse when exposed to the sun.

This medicine may increase your risk for fundic gland polyps (abnormal tissue growth in the upper part of your stomach). This is more likely if you are receiving this medicine for more than 1 year. Talk to your doctor if you have concerns.

Do not Stop taking omeprazole without first checking with your doctor, or unless told to do so by your doctor.

Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before you have medical tests.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription (eg, atazanavir, nelfinavir, Reyataz®, Viracept®) or nonprescription (over-the-counter [OTC]) medicines and herbal (eg, St. John's wort) or vitamin supplements.

Common side effects of Prilosec OTC

Some side effects of omeprazole may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Serious side effects of Prilosec OTC

Along with its needed effects, omeprazole may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking omeprazole:

Get emergency help immediately if any of the following symptoms of overdose occur while taking omeprazole:

Symptoms of overdose

• blurred vision
• confusion
• dryness of the mouth
• flushing
• headache
• increased sweating

For healthcare professionals

Applies to omeprazole: compounding powder, oral delayed release capsule, oral delayed release tablet, oral powder for reconstitution, oral powder for reconstitution delayed release, oral suspension, oral tablet disintegrating delayed release.

General adverse events

The most commonly reported side effects included headache, abdominal pain, nausea, and diarrhea.^[Ref]

Other

• Very common (10% or more): Fever (up to 33%), otitis media (up to 22%)
• Common (1% to 10%): Accidental injury, asthenia
• Uncommon (0.1% to 1%): Malaise
• Very rare (less than 0.01%): Elevated body temperature
• Postmarketing reports: Pain, fatigue, tinnitus^[Ref]

Otitis media occurred most frequently in patients 1 month to less than 1 year of age.

Fever most commonly occurred in patients 1 to less than 2 years of age.

Accidental injury most commonly occurred in patients 2 to 16 years of age.^[Ref]

Respiratory

• Very common (10% or more): Respiratory system reactions (up to 75%)
• Common (1% to 10%): Cough, pharyngitis/pharyngeal pain, rhinitis, upper respiratory infection
• Rare (0.01% to 0.1%): Bronchospasm
• Very rare (less than 0.01%): Dyspnea
• Postmarketing reports: Epistaxis^[Ref]

Patients 1 to less than 2 years of age had the highest frequency of adverse reactions of the respiratory system, followed by patients 1 month to less than 1 year and patients 2 to 16 years of age.^[Ref]

Nervous system

• Very common (10% or more): Taste perversion (up to 15%)
• Common (1% to 10%): Dizziness, drowsiness, headache, somnolence
• Uncommon (0.1% to 1%): Paresthesia, taste disturbances, vertigo
• Rare (0.01% to 0.1%): Hepatic encephalopathy, lightheadedness
• Postmarketing reports: Tremor^[Ref]

Lightheadedness occurred predominantly in severely ill or elderly patients.

Taste disturbance usually resolved when treatment was stopped.

Taste perversion most commonly occurred in patients given concomitant treatment with clarithromycin.

Hepatic encephalopathy occurred in patients with preexisting liver disease.^[Ref]

Gastrointestinal

• Very common (10% or more): Diarrhea (Up to 14%)
• Common (1% to 10%): Abdominal pain, acid regurgitation, benign fundic gland polyps, constipation, flatulence, nausea, tongue discoloration, vomiting
• Rare (0.01% to 0.1%): Dry mouth, gastrointestinal candidiasis, microscopic colitis, stomatitis
• Very rare (less than 0.01%): Dyspepsia, hemorrhagic necrotic gastritis
• Postmarketing reports: Abdominal swelling, Clostridium difficile associated diarrhea, esophageal candidiasis, fecal discoloration, fundic gland polyps, irritable colon, mucosal atrophy of the tongue, pancreatitis (sometimes fatal)^[Ref]

Hemorrhagic necrotic gastritis has been reported in pediatric patients.

Diarrhea most commonly occurred in patients given concomitant treatment with clarithromycin and amoxicillin.

Benign gastric fundic gland polyps appeared to be reversible when omeprazole was discontinued.^[Ref]

Dermatologic

• Common (1% to 10%): Rash
• Uncommon (0.1% to 1%): Alopecia, dermatitis, erythema multiforme, increased sweating, pruritus, photosensitivity, skin eruptions, urticaria
• Rare (0.01% to 0.1%): Allergic vasculitis, Stevens-Johnson syndrome, toxic epidermal necrolysis (some fatal)
• Frequency not reported: Subacute cutaneous lupus erythematosus
• Postmarketing reports: Cutaneous lupus erythematosus, dry skin, hyperhidrosis, petechia, skin inflammation, severe generalized skin reactions, systemic lupus erythematosus^[Ref]

Musculoskeletal

• Common (1% to 10%): Back pain
• Uncommon (0.1% to 1%): Fracture of the hip/wrist/spine
• Rare (0.01% to 0.1%): Arthralgia, joint pain, muscular weakness, myalgia
• Postmarketing reports: Bone fracture, leg pain, muscle cramps^[Ref]

Psychiatric

• Common (1% to 10%): Insomnia
• Rare (0.01% to 0.1%): Aggression, agitation, confusion/reversible mental confusion, depression, hallucinations
• Postmarketing reports: Anxiety, apathy, dream abnormalities, nervousness, psychiatric and sleep disturbances^[Ref]

Confusion, agitation, aggression, depression, and hallucinations occurred predominantly in severely ill or elderly patients.^[Ref]

Immunologic

• Common (1% to 10%): Flu syndrome^[Ref]

Hepatic

• Uncommon (0.1% to 1%): Increased liver enzymes (ALT, alkaline phosphatase, AST, bilirubin, gamma glutamyl transferase)
• Rare (0.01% to 0.1%): Hepatic failure, hepatitis with/without jaundice
• Postmarketing reports: Cholestatic disease, fatal hepatic failure, hepatocellular disease, jaundice, liver disease, liver necrosis (some fatal), mixed hepatitis^[Ref]

Cardiovascular

• Uncommon (0.1% to 1%): Peripheral edema
• Postmarketing reports: Bradycardia, chest pain/angina, elevated blood pressure/hypertension, palpitations, tachycardia^[Ref]

Peripheral edema usually resolved when treatment was stopped.^[Ref]

Hematologic

• Rare (0.01% to 0.1%): Agranulocytosis, hypochromic/microcytic anemia, leukopenia, pancytopenia, thrombocytopenia
• Postmarketing reports: Anemia, fatal agranulocytosis, hemolytic anemia, leukocytosis, neutropenia, purpura^[Ref]

Hypersensitivity

• Rare (0.01% to 0.1%): Anaphylactic reaction/shock, angioedema, hypersensitivity reactions
• Postmarketing reports: Anaphylaxis^[Ref]

Metabolic

• Rare (0.01% to 0.1%): Hyponatremia
• Very rare (less than 0.01%): Hypocalcemia, hypokalemia, hypomagnesemia with/without hypocalcemia and/or hypokalemia, weight increase
• Postmarketing reports: Anorexia, cyanocobalamin (vitamin B12) deficiency, hypoglycemia^[Ref]

Severe hypomagnesemia may result in hypocalcemia, and this condition may be associated with hypokalemia.

Hypokalemia was reported in pediatric patients.^[Ref]

Renal

• Rare (0.01% to 0.1%): Interstitial nephritis
• Very rare (less than 0.01%): Impaired renal function, nephrosis
• Postmarketing reports: Elevated serum creatinine, glycosuria^[Ref]

Ocular

• Rare (0.01% to 0.1%): Blurred vision
• Frequency not reported: Irreversible visual impairment
• Postmarketing reports: Anterior ischemic optic neuropathy, double vision, dry eye syndrome, ocular irritation, optic atrophy, optic neuritis^[Ref]

Irreversible visual impairment has been reported in critically ill patients who generally received high doses of the IV formulation as a bolus; however, no causal relationship has been established.^[Ref]

Endocrine

• Rare (0.01% to 0.1%): Gynecomastia^[Ref]

Genitourinary

• Very rare (less than 0.01%): Impotence
• Postmarketing reports: Hematuria, microscopic pyuria, proteinuria, testicular pain, urinary frequency, urinary tract infection^[Ref]

A causal relationship between this drug and impotence has not been established.^[Ref]

Oncologic

• Postmarketing reports: Gastroduodenal carcinoids^[Ref]

Gastroduodenal carcinoids have been reported in patients with Zollinger-Ellison syndrome on long-term therapy. This condition may be a manifestation of the underlying condition, which is known to be associated with tumors.^[Ref]

See also:

Frequently asked questions

• Is famotidine safer than omeprazole for heartburn?
• Pantoprazole vs. omeprazole: What's the difference between them?
• What foods should I avoid when taking omeprazole?
• Can you take an antacid with omeprazole?
• Can I take omeprazole in the morning and famotidine at night?
• Is omeprazole (Prilosec) bad for your kidneys?
• Does omeprazole cause cancer?
• How soon after taking levothyroxine can I take omeprazole?

Further information

Prilosec OTC side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer