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Prilosec OTC Side Effects

Generic Name: omeprazole

Note: This page contains side effects data for the generic drug omeprazole. It is possible that some of the dosage forms included below 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

As well as its needed effects, omeprazole (the active ingredient contained in Prilosec OTC) may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking omeprazole, check with your doctor immediately:

  • 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

If any of the following symptoms of overdose occur while taking omeprazole, get emergency help immediately:

Symptoms of overdose:
  • Blurred vision
  • confusion
  • dryness of the mouth
  • flushing
  • headache
  • increased sweating

Minor Side Effects

Some omeprazole side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:
  • Body aches or pain
  • chest pain
  • constipation
  • cough
  • diarrhea or loose stools
  • difficulty with breathing
  • dizziness
  • ear congestion
  • gas
  • heartburn
  • loss of voice
  • muscle pain
  • nasal congestion
  • runny nose
  • sneezing
  • unusual drowsiness

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.[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
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
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, gastric fundic gland polyps[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 were rarely reported, and 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
Frequency not reported: Adverse reactions of the respiratory system
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
Uncommon (0.1% to 1%): Malaise
Rare (0.01% to 0.1%): Fever
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
Rare (0.01% to 0.1%): Photosensitivity, 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[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]

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


Very rare (less than 0.01%): Gynecomastia[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 cause tumors.[Ref]

Postmarketing reports: Gastroduodenal carcinoids[Ref]


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

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

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

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

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

It is possible that some side effects of Prilosec OTC may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.