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New proton pump inhibitor by AstraZeneca girds for battle against GERD

With the patent clock ticking on AstraZeneca's Prilosec (omeprazole), the Food & Drug Administration has approved the manufacturer's follow-up proton pump inhibitor (PPI) Nexium (esomeprazole magnesium).

Esomeprazole was developed as the optical isomer of omeprazole. Like other PPIs, esomeprazole suppresses gastric acid secretion by specific inhibition of the H+/K+ - ATPase in the gastric parietal cell. By acting specifically on the proton pump, esomeprazole blocks the final step in acid production, thus reducing gastric acidity.

The FDA has approved esomeprazole for the following indications:

• Healing and symptomatic resolution of heartburn and other symptoms associated with gastroesophageal reflux disease (GERD)

• Short-term treatment (four to eight weeks) in symptom resolution and healing of erosive esophagitis (EE)

• Maintenance of both healing and symptom resolution in EE (controlled studies do not extend beyond six months)

• In combination with amoxicillin and clarithromycin, for the treatment of patients with H. pylori infection and duodenal ulcer disease to eradicate H. pylori and reduce the risk of duodenal ulcer recurrence

Esomeprazole joins four other PPIs currently on the market—omeprazole (Prilosec, AstraZeneca), lansoprazole (Prevacid, TAP Pharmaceuticals), rabeprazole (Aciphex, Eisai/Janssen), and pantoprazole (Protonix, Wyeth-Ayerst). So what differentiates esomeprazole from these other PPIs? According to Doug Levine, M.D., chief medical officer at AstraZeneca, "Nexium is not just another PPI." He said esomeprazole "represents a new technology in drug development," which, in comparative studies, "consistently showed improvement over omeprazole in the proportionate number of patients [with EE] who are completely healed." This finding is significant, said Levine, because when the other PPIs were compared against omeprazole in these same patients with EE, "they did not show any difference in the proportionate number of patients healed."

Joseph Reilly, Pharm.D., concurred that "based on the preliminary data, esomeprazole is more potent at raising the gastric pH and will provide better symptom relief and possibly better healing over omeprazole 20 mg." He is an assistant professor of pharmacy practice at Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Brooklyn, N.Y., who specializes in gastroenterology. Whether esomeprazole holds an advantage over the other PPIs besides omeprazole remains to be seen, according to Reilly.

Mary Lee Harper, Pharm.D., director of the University of Kentucky Drug Information Center, believes that for the "10%-15%" subset of patients who are not responding to current therapies or who require a twice-daily regimen with omeprazole to achieve symptom control, esomeprazole may be the answer.

Esomeprazole is the first PPI to be approved by the FDA based on clinical trials using another PPI as an active control. Results from these trials showed higher healing rates with esomeprazole 40 mg (94.1%) and esomeprazole 20 mg (89.9%), as compared with omeprazole 20 mg (86.9%) after eight weeks of treatment.

The safety profile of esomeprazole was evaluated in more than 10,000 patients in clinical trials worldwide, involving various dosages and durations of treatment. The most frequently reported adverse events were headache and diarrhea. Nausea, flatulence, abdominal pain, constipation, and dry mouth occurred at similar rates among patients taking either esomeprazole or omeprazole.

By inhibiting gastric acid secretion, esomeprazole and other PPIs may interfere with the absorption of drugs for which gastric pH determines bioavailability, such as ketoconazole, iron salts, and digoxin. Like the other PPIs, esomeprazole inhibits the cytochrome P450 system, and dose adjustments of some concomitantly given drugs may be required.

The wholesaler acquisition cost for esomeprazole is $3.33/capsule for the 20- and 40-mg capsules, according to AstraZeneca. The product is expected to be available this month.

Tammy Chernin, R.Ph.

TIPS TO REMEMBER: Nexium

• Nexium should be taken at least one hour before meals.

• Antacids may be used while taking Nexium.

• For patients who have difficulty swallowing capsules, the contents of one Nexium capsule can be mixed with one tablespoon of applesauce, then swallowed immediately. The pellets should not be chewed or crushed, nor should the mixture be stored for future use.

 

Tammy Chernin. New proton pump inhibitor by AstraZeneca girds for battle against GERD. Drug Topics 2001;6:10.