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Prilosec OTC Side Effects

Generic name: omeprazole

Medically reviewed by Last updated on Feb 5, 2024.

Note: This document contains side effect information about omeprazole. Some dosage forms listed on this page may not apply 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.

Serious side effects of Prilosec OTC

Along with its needed effects, omeprazole (the active ingredient contained in Prilosec OTC) 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:


Incidence not known

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

Symptoms of overdose

Other 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:

Less common

Incidence not known

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.


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

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]


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]


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]


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]


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]


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

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]


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


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]


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

Uncommon (0.1% to 1%): Peripheral edema

Postmarketing reports: Bradycardia, chest pain/angina, elevated blood pressure/hypertension, palpitations, tachycardia[Ref]


Rare (0.01% to 0.1%): Agranulocytosis, hypochromic/microcytic anemia, leukopenia, pancytopenia, thrombocytopenia

Postmarketing reports: Anemia, fatal agranulocytosis, hemolytic anemia, leukocytosis, neutropenia, purpura[Ref]


Rare (0.01% to 0.1%): Anaphylactic reaction/shock, angioedema, hypersensitivity reactions

Postmarketing reports: Anaphylaxis[Ref]


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]


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]


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]


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


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]


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]

Frequently asked questions


1. (2022) "Product Information. PriLOSEC (omeprazole)." Merck & Co., Inc

2. (2003) "Product Information. Omeprazole (omeprazole)." Mylan Pharmaceuticals Inc

3. Cerner Multum, Inc. "UK Summary of Product Characteristics."

4. Cerner Multum, Inc. "Australian Product Information."

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.