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Omesec Side Effects

Generic name: omeprazole

Medically reviewed by Last updated on Jun 30, 2021.

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 Omesec.

For the Consumer

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

Side effects requiring immediate medical attention

Along with its needed effects, omeprazole (the active ingredient contained in Omesec) 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
  • itching, skin rash
  • joint pain
  • loss of appetite
  • muscle aches or cramps
  • pain
  • red or irritated eyes
  • redness, tenderness, itching, burning, or peeling of the skin
  • 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

  • Blistering, peeling, or loosening of the skin
  • drowsiness
  • fast, racing, or uneven heartbeat
  • mood or mental changes
  • muscle spasms (tetany) or twitching seizures
  • nausea
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • trembling
  • vomiting

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

Side effects not requiring immediate medical attention

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]


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]


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]

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]

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%): 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]


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 (the active ingredient contained in Omesec) was discontinued.[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]


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]


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]


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

More about Omesec (omeprazole)

Consumer resources

Other brands
Prilosec, Prilosec OTC

Professional resources

Related treatment guides


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.