Omeprazole Side Effects

Omeprazole Side Effects

Omeprazole is a proton pump inhibitor. It is used to block the production of stomach acid. Omeprazole is prescribed to patients suffering from dyspepsia, heartburn, erosive esophagitis, stress ulcer, peptic ulcer disease of the stomach and duodenum, stomach bleeding, systemic mastocytosis, multiple endocrine adenomas, benign tumors of hormone producing glands, gastroesophageal reflux disease, laryngopharyngeal reflux and Zollinger–Ellison syndrome, pancreatitis, fatty bowel movements in cystic fibrosis. The drug can also be used to facilitate healing of erosive esophagitis, to prevent recurrence of ulcer and bleeding in critical patients and patients who use Aspirin/Ibuprofen drugs, and for prophylaxis of Mendelson syndrome (acid aspiration). Omeprazole is part of a combination developed for treatment of gastric ulcer caused by Helicobacter pylori (H. pylori) infection.
Read also Omeprazole Drug Information

Side effects

According to studies, up to 6.9% of patients who use Omeprazole experience different side effects and some of them can be quite serious.

The most common adverse effects of Omeprazole include but not limited to:

  • Headache
  • General feeling of being unwell
  • Dizziness
  • Confusion
  • Lightheadedness
  • Tiredness
  • Asthenia
  • Muscle weakness
  • Upper respiratory infection (fever, chills, sore throat)
  • Cough
  • Acute pneumonia
  • Chest pain
  • Angina
  • Palpitations
  • Arrhythmia (fast, slow, or irregular heartbeat)
  • Elevated blood pressure
  • Peripheral edema (swelling of the extremities)
  • Inflammation of the mouth
  • Dry mouth
  • Stomatitis
  • Vomiting
  • Abdominal pain
  • Belching
  • Heartburn
  • Acid regurgitation
  • Nausea
  • Gastrointestinal infections
  • Diarrhea
  • Constipation
  • Irritable colon
  • Fecal discoloration
  • Flatulence
  • Unusual or sudden weight increase
  • Back pain
  • Leg pain
  • Depression
  • Nervousness
  • Anxiety
  • Apathy
  • Insomnia
  • Somnolence
  • Vision changes (blurred vision, double vision)
  • Dry eye syndrome
  • Ocular irritation
  • Rash (petechiae; purpura)
  • Photosensitivity
  • Red, swollen, blistered, or peeling skin
  • Yellowing of the eyes or skin

People who use Omeprazole can also experience other side effects such as:

  • Skin inflammation
  • Erythema multiforme
  • Tremors
  • Tinnitus
  • Taste perversion
  • Hemifacial dysesthesia
  • Numbness of the extremities
  • Paresthesia
  • Ataxia
  • Vertigo
  • Myalgia
  • Muscle cramps
  • Bone pain
  • Joint pain
  • Bone fracture
  • Urinary tract infection
  • Frequent urination
  • Testicular pain
  • Impotence
  • Gynecomastia
  • Breast enlargement in women
  • Breast tenderness
  • A dose-dependent reduction in protein-bound cyanocobalamin absorption
  • Osteoporosis due to poor absorption of calcium

Like any other drug, Omeprazole can cause allergic reactions that manifests as rash, hives, itching, breathing difficulty, bronchospasm, unusual hoarseness, chest tightness, anaphylaxis, anaphylactic shock, swelling of the eyes, mouth, face, lips, tongue or throat, angioedema, interstitial nephritis, fever, pain, fatigue, malaise.

In some rare cases, Omeprazole can also cause toxic (toxic epidermal necrolysis (sometimes fatal), Stevens-Johnson syndrome) and autoimmune reactions (fever, arthralgias, Raynaud’s phenomenon with a positive ANA titer).

All these reactions are serious and require urgent medical attention and help.

Rare side effects

In some rare cases, Omeprazole can lead to campylobacter gastroenteritis, pruritus, alopecia, dry skin, hyperhidrosis, dermatomyositis, cutaneous leukocytoclastic vasculitis, gastric benign fundic gland polyps and hyperplasia of gastric enterochromaffin cells development.

Omeprazole can cause development of gastroduodenal carcinoids and persistent achlorhydria in patients with Zollinger-Ellison syndrome.

Changes in laboratory tests

If you are taking Omeprazole, your blood tests may reveal some changes but you should keep in mind that the drug can cause such changes as elevations in liver function tests (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, γ-glutamyl transpeptidase, bilirubin), uric acid, serum creatinine and plasma gastrin levels. Besides, blood tests may reveal changes in microelements levels such as hypomagnesemia (that can manifest as seizures, dizziness, abnormal, fast or skipped heartbeat, jitteriness, jerking movements or tremors, muscle weakness, spasms of the hands and feet, cramps or muscle aches, and spasm of the voice box), hyponatremia, hypokalemia and hypocalcemia.

And patients with diabetes should keep in mind that it causes hypoglycemia.

Theses changes are reversible and disappear after discontinuation of Omeprazole.

Omeprazole can also cause some changes in hematological tests: hemolytic anemia, neutropenia, leukopenia, leucocytosis,  agranulocytosis (sometimes fatal), thrombocytopenia, pancytopenia.

Urine tests may reveal such changes as proteinuria, hematuria, glycosuria, microscopic pyuria.

Serious side effects

Omeprazole can cause serious side effects that would make patients appeal for urgent medical help.

These serious side effects include:

  • Epistaxis
  • Mucosal atrophy of the tongue
  • Esophageal candidiasis
  • Severe stomach pain or cramps
  • Gastrointestinal infections
  • Severe diarrhea
  • Hepatic failure (sometimes fatal)
  • Liver necrosis (sometimes fatal)
  • Hepatic encephalopathy
  • Hepatocellular disease
  • Cholestatic disease
  • Mixed hepatitis
  • Pancreatitis (sometimes fatal)
  • Interstitial nephritis
  • Renal failure
  • Angina
  • Arrhythmias (tachycardia, bradycardia, palpitations)
  • Abdominal swelling
  • Swelling of the hands, ankles, or feet
  • Optic atrophy
  • Anterior ischemic optic neuropathy
  • Optic neuritis
  • Agitation
  • Aggression
  • Hallucinations
  • Seizures
  • Disseminated epidermal necrosis
  • Furunculosis
  • Exfoliative dermatitis
  • Unusual bruising or bleeding
  • Gynecomastia
  • Nonspecific polyarthritis
  • Hip and other bone fractures
  • Acute severe myopathy
  • Blood and bone marrow problems
  • Acute pneumonia

Side effects in pregnant women

Omeprazole is contraindicated to pregnant women but experimental studies did not show any toxic effect of this medicine on pregnancy.

Side effects in children

Omeprazol’s side effects in children are similar to those of adults but such problems as respiratory symptoms (cough, chest pain, wheezing) are more frequent.


You may never experience any of the side effects listed above. Your doctor cannot predict your body’s reaction to Omeprazole until you have tried it. That is why you should immediately inform your doctor of any changes in your health condition after taking Omeprazole. Therefore, when you feel something is wrong, ask your doctor for advice and he or she will diagnose if your problem is connected with the medicine intake. You should also be careful because some of the side effects of Omeprazole require urgent medical attention.