Since omeprazole is metabolised by CYP2C19 and CYP3A4, active substances known to inhibit CYP2C19 or CYP3A4 (such as clarithromycin and voriconazole) may lead to increased omeprazole serum levels by decreasing omeprazole's rate of metabolism. Concomitant voriconazole treatment resulted in more than doubling of the omeprazole exposure. As high doses of omeprazole have been well tolerated adjustment of the omeprazole dose is not generally required. However, dose adjustment should be considered in patients with severe hepatic impairment and if long-term treatment is indicated.

Inducers of CYP2C19 and/or CYP3A4

Active substances known to induce CYP2C19 or CYP3A4 or both (such as rifampicin and St John's wort) may lead to decreased omeprazole serum levels by increasing omeprazole's rate of metabolism.

4.6 Pregnancy and lactation

 Results from three prospective epidemiological studies (more than 1000 exposed outcomes) indicate no adverse effects of omeprazole on pregnancy or on the health of the foetus/newborn child). Omeprazole can be used during pregnancy.

Omeprazole is excreted in breast milk but is not likely to influence the child when therapeutic doses are used.

4.7 Effects on ability to drive and use machines

 Ulcid is not likely to affect the ability to drive or use machines. Adverse drug reactions such as dizziness and visual disturbances may occur (see section 4.8). If affected, patients should not drive or operate machinery,

4.8 Undesirable effects

 The most common side effects (1-10% of patients) are headache, abdominal pain, constipation, diarrhea, flatulence and nausea/vomiting.

The following adverse drug reactions have been identified or suspected in the clinical trials programme for omeprazole and post-marketing. None was found to be dose-related. Adverse reactions listed below are classified according to frequency and System Organ Class (SOC). Frequency categories are defined according to the following convention: Very common ( 1/10), Common ( 1/100 to < 1/10), Uncommon ( 1/1,000 to < 1/100), Rare ( 1/10,000 to < 1/1,000), Very rare (< 1/10,000), Not known (cannot be estimated from the data available).

SOC/frequency
 Adverse reaction
 
Blood and lymphatic system disorders
 
Rare:
 Leukopenia, thrombocytopenia
 
Very rare:
 Agranulocytosis, pancytopenia
 
Immune system disorders
 
Rare:
 Hypersensitivity reactions e.g. fever, angioedema and anaphylactic reaction/shock
 
Metabolism and nutrition disorders
 
Rare:
 Hyponatraemia
 
Very rare:
 Hypomagnesaemia
 
Psychiatric disorders
 
Uncommon:
 Insomnia
 
Rare:
 Agitation, confusion, depression
 
Very rare:
 Aggression, hallucinations
 
Nervous system disorders
 
Common:
 Headache
 
Uncommon:
 Dizziness, paraesthesia, somnolence
 
Rare:
 Taste disturbance
 
Eye disorders
  
Rare:
 Blurred vision
 
Ear and labyrinth disorders
 
Uncommon:
 Vertigo
 
Respiratory, thoracic and mediastinal disorders
 
Rare:
 Bronchospasm
 
Gastrointe