<p><strong>Severe or irreversible adverse effects</strong>: The possible induction of carcinoid tumors by profound acid suppression, and a rise in serum gastrin may occur. There is a rise in serum gastrin levels in the first 3 months of treatment, which are then maintained though at a lower level than those found in pernicious anaemia. Long term treatment with a proton pump inhibitor in patients with Helicobacter pylori infection may accelerate the development of atrophic gastritis.<br />
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<strong>Symptomatic adverse effect</strong>: Dose dependent diarrhoea occurs with an incidence of about 4% at 30 mg per day, rising to 8% at 60 mg per day. Headache occurs in 2-3% of treated patients.</p>