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Prilosec OTC Side Effects

Generic Name: omeprazole

Note: This document contains side effect information about omeprazole. Some of the dosage forms listed on this page may not apply to the brand name Prilosec OTC.

For the Consumer

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

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:


  • Back, leg, or stomach pain
  • bleeding or crusting sores on the lips
  • blisters
  • bloody or cloudy urine
  • chills
  • continuing ulcers or sores in the mouth
  • difficult, burning, or painful urination
  • fever
  • frequent urge to urinate
  • general feeling of discomfort or illness
  • joint pain
  • loss of appetite
  • muscle aches or cramps
  • pain
  • red or irritated eyes
  • redness, tenderness, itching, burning, or peeling of the skin
  • skin rash or itching
  • sore throat
  • sores, ulcers, or white spots on the lips, in the mouth, or on the genitals
  • unusual bleeding or bruising
  • unusual tiredness or weakness

Incidence Not Known

  • Drowsiness
  • fast, racing, or uneven heartbeat
  • mood or mental changes
  • muscle spasms (tetany) or twitching seizures
  • nausea or vomiting
  • trembling

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

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

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


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

Nervous system

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): Taste perversion (Up to 15%)

Common (1% to 10%): Headache, drowsiness, somnolence, dizziness

Uncommon (0.1% to 1%): Paresthesia, vertigo, taste disturbances

Rare (0.01% to 0.1%): Lightheadedness, hepatic encephalopathy

Postmarketing reports: Tremor[Ref]


Very common (10% or more): Diarrhea (Up to 14%)

Common (1% to 10%): Abdominal pain, constipation, flatulence, nausea/vomiting, acid regurgitation, tongue discoloration, benign fundic gland polyps

Rare (0.01% to 0.1%): Dry mouth, stomatitis, gastrointestinal candidiasis, microscopic colitis

Very rare (less than 0.01%): Dyspepsia, hemorrhagic necrotic gastritis

Postmarketing reports: Pancreatitis (sometimes fatal), irritable colon, fecal discoloration, esophageal candidiasis, mucosal atrophy of the tongue, Clostridium difficile associated diarrhea, abdominal swelling[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%): Upper respiratory infection, cough, rhinitis, pharyngitis/pharyngeal pain

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]


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]

Common (1% to 10%): Asthenia, flu-syndrome, fever

Uncommon (0.1% to 1%): Malaise

Very rare (less than 0.01%): Elevated body temperature

Frequency not reported: Otitis media, accidental injury

Postmarketing reports: Pain, fatigue, tinnitus[Ref]


Common (1% to 10%): Rash

Uncommon (0.1% to 1%): Dermatitis, alopecia, skin eruptions, erythema multiforme, urticaria and/or pruritus, photosensitivity

Rare (0.01% to 0.1%): Increased sweating/hyperhidrosis, Stevens-Johnson syndrome, toxic epidermal necrolysis (some fatal)

Frequency not reported: Subacute cutaneous lupus erythematosus

Postmarketing reports: Severe generalized skin reactions, skin inflammation, petechia, dry skin, systemic lupus erythematosus[Ref]


Common (1% to 10%): Insomnia

Rare (0.01% to 0.1%): Agitation, confusion/reversible mental confusion, depression, aggression, hallucinations

Postmarketing reports: Anxiety, apathy, nervousness, dream abnormalities, psychiatric and sleep disturbances[Ref]

Confusion, agitation, aggression, depression, and hallucinations occurred predominantly in severely ill or elderly patients.[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, myalgia, muscular weakness, joint pain

Postmarketing reports: Muscle cramps, leg pain, bone fracture[Ref]


Uncommon (0.1% to 1%): Increased liver enzymes (ALT, AST, GGT, alkaline phosphatase, bilirubin)

Rare (0.01% to 0.1%): Hepatitis with/without jaundice, hepatic failure/encephalopathy

Postmarketing reports: Liver disease, fatal hepatic failure, liver necrosis (some fatal), hepatocellular disease, cholestatic disease, mixed hepatitis, jaundice[Ref]


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

Uncommon (0.1% to 1%): Peripheral edema

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


Rare (0.01% to 0.1%): Leukopenia, thrombocytopenia, agranulocytosis, pancytopenia, hypochromic/microcytic anemia

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


Rare (0.01% to 0.1%): Hypersensitivity reactions, angioedema, anaphylactic reaction/shock, allergic vasculitis[Ref]


Rare (0.01% to 0.1%): Hyponatremia

Very rare (less than 0.01%): Weight increase, hypomagnesemia with/without hypocalcemia and/or hypokalemia, hypokalemia

Frequency not reported: Hypocalcemia

Postmarketing reports: Anorexia, hypoglycemia[Ref]

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

Hypokalemia was reported in pediatric patients.[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%): Blurred vision

Frequency not reported: Irreversible visual impairment

Postmarketing reports: Optic atrophy, anterior ischemic optic neuropathy, optic neuritis, dry eye syndrome, ocular irritation, double vision[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]


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

Very rare (less than 0.01%): Impotence

Postmarketing reports: Hematuria, proteinuria, microscopic pyuria, urinary tract infection, urinary frequency, testicular pain[Ref]


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


1. Cerner Multum, Inc. "Australian Product Information." O 0

2. "Product Information. Zegerid (omeprazole)." Santarus Inc, San Diego, CA.

3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

4. "Product Information. Prilosec (omeprazole)." Merck & Co, Inc, West Point, PA.

5. "Product Information. Omeprazole (omeprazole)." Mylan Pharmaceuticals Inc, Morgantown, WV.

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.