The most common symptoms that were reported in clinical trials with omeprazole have been gastrointestinal eg, diarrhoea, nausea and constipation, and also headache, each in 1-3%.
Adverse effects are listed by organ system and frequency with the following convention: Common (>1/100, <1/100), less common (>1/1000, <1/100), rare (>1/10,000, <1/1000).
Common: Headache. Less Common: Fatigue. Rare: Increased sweating, peripheral oedema, hyponatraemia, hypersensitivity reactions eg, angioedema, fever and anaphylactic shock.
Rare: Leucopenia, thrombocytopenia, agranulocytosis, pancytopenia.
Common: Diarrhoea, nausea/vomiting, constipation, abdominal pain, flatulence. Rare: Dry mouth, taste disturbances, stomatitis, candidiasis.
Less Common: Rash, pruritus, urticaria, dermatitis. Rare: Hair loss, photosensitivity, erythema multiforme.
Less Common: Change in liver function tests. Rare: Encephalopathy in patients with severe hepatic disease, hepatitis with or without jaundice, liver failure.
Rare: Arthralgia, myalgia, muscle weakness.
Less Common: Paraesthesia, dizziness, drowsiness.
Less Common: Sleep disturbance. Rare: Reversible confusion, agitation, depression, aggression and hallucinations, especially in severely ill patients.
Rare: Interstitial nephritis.
Rare: Blurred vision.
Isolated cases of Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported, but a relationship with omeprazole could not be established.
In clinical trials, an increased frequency of adverse reactions involving the central nervous system (especially headache) and gastrointestinal adverse reactions have been observed when omeprazole was given together with clarithromycin.
During post-approval use of omeprazole, cases of Clostridium difficile
-associated diarrhoea and bone fractures have been reported (frequency unknown).