Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Nexium (AstraZeneca)
20 mg and 40 mg tablets
Approved indications: peptic ulcer, gastro-oesophageal reflux disease
Australian Medicines Handbook Section 12.1.4

Omeprazole is the most frequently prescribed proton pump inhibitor in a market worth nearly $250 million. Its patent recently expired, but the manufacturers have now marketed esomeprazole. This is the S-isomer of the omeprazole molecule. Esomeprazole acts in the same way as omeprazole by inhibiting the proton pump in the parietal cells of the stomach (see 'Drugs that inhibit acid secretion' Aust Prescr 2000;23:57-9). In patients with gastro-oesophageal reflux disease esomeprazole 20 mg will keep the intragastric pH above pH4 for at least 16 hours in 24% of patients, compared with 14% of patients given omeprazole 20 mg.

In addition to the initial and maintenance treatment of patients with erosive oesophagitis, esomeprazole has also been approved for use in the treatment of peptic ulcers. It can be combined with amoxycillin and clarithromycin to eradicate Helicobacter pylori in patients with active or healed ulcers. A one week course of this combination is as effective, at healing duodenal ulcers associated with H. pylori, as a combination of omeprazole and antibiotics followed by a further three weeks of omeprazole. (Although a shorter course of treatment would be helpful, the trial did not study the outcome of giving omeprazole and antibiotics for just one week. As different regimens were compared it is difficult to draw conclusions about any difference between the drugs.)

The common adverse effects of esomeprazole include headache, diarrhoea, nausea and vomiting. Esomeprazole is metabolised by cytochrome P450 2C19 and 3A4 so there is a potential for interactions. Known interacting drugs include diazepam, cisapride, clarithromycin, citalopram, imipramine and phenytoin. Severe liver disease reduces the clearance of esomeprazole.

While esomeprazole has more effect on intragastric pH than omeprazole, this may not confer a significant clinical advantage. After eight weeks of treatment, a daily 20 mg dose of either drug will have healed more than 80% of patients with erosive oesophagitis. However, the manufacturers recommend using esomeprazole 40 mg for this indication. This higher dose will heal 68-78% of patients after four weeks and 87-90% after eight weeks.

Although esomeprazole has been approved for the symptomatic treatment of gastro-oesophageal reflux disease, it is not a first-line treatment for heartburn.1