Esomeprazole

Esomeprazole
Systematic (IUPAC) name
(S)-5-methoxy-2-[(4-methoxy-3,5-dimethylpyridin-2-yl) methylsulfinyl]-3H-benzoimidazole
Identifiers
CAS number	119141-88-7
ATC code	A02BC05
PubChem	4594
DrugBank	APRD00363
ChemSpider	7843322
Chemical data
Formula	C17H19N3O3S
Mol. mass	345.417 g/mol
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	50 to 90%
Metabolism	Hepatic (CYP2C19, CYP3A4)
Half life	1–1.5 hours
Excretion	80% Renal 20% faecal
Therapeutic considerations
Pregnancy cat.	B3(AU)
Legal status	Prescription Only (S4)(AU) POM(UK) ℞-only(US)
Routes	Oral, IV

Esomeprazole (pronounced /iːsɵˈmɛprəzoʊl/) is a proton pump inhibitor (brand names Sompraz, Zoleri, Nexium, Lucen, Esopral; Axagon in Italy, Nexiam in Belgium) developed and marketed by AstraZeneca which is used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome. Esomeprazole is the S-enantiomer of omeprazole (marketed as Losec/Prilosec), and AstraZeneca claims improved efficacy of this single enantiomer product over the racemic mixture of omeprazole. However, this greater efficacy has been disputed, with some claiming it offers no benefit from its older form.

Pharmacology

Esomeprazole is a proton pump inhibitor which reduces gastric acid secretion through inhibition of H⁺/K⁺-ATPase in gastric parietal cells. By inhibiting the functioning of this enzyme, the drug prevents formation of gastric acid.

Clinical use

Use in Helicobacter pylori eradication

Esomeprazole is combined with the antibiotics clarithromycin and amoxicillin (or metronidazole) in the 7-day eradication triple therapy for Helicobacter pylori. Infection by H. pylori is the causative factor in the majority of peptic and duodenal ulcers.

Evidence of efficacy

AstraZeneca claims that esomeprazole provides improved efficacy, in terms of stomach acid control, over racemic omeprazole. Many health professionals have expressed the view that this improvement in efficacy is due to the dose of esomeprazole recommended for therapy rather than any superiority of esomeprazole per se.

An alternative rationale suggested for the use of esomeprazole was the reduction in interindividual variability in efficacy. However the clinical advantage of this hypothesis has not thoroughly been tested in large-scale trials.^[1]

Given the large difference in cost between all other proton pump inhibitors and that of Prilosec-OTC (equivalent to omeprazole 20mg), many physicians recommend a trial of over-the-counter products before beginning more extensive therapies and testing.

Although the (S)-isomer is more potent in humans, the (R)-isomer is more potent in the testing of rats, while the enantiomers are equipotent in dogs.^[2]

Dosage forms

Esomeprazole is available as delayed-release capsules in the United States or as delayed release tablets in Australia and Canada (containing esomeprazole magnesium) in strengths of 20 mg and 40 mg; and as esomeprazole sodium for intravenous injection/infusion. Oral esomeprazole preparations are enteric-coated, due to the rapid degradation of the drug in the acidic conditions of the stomach. This is achieved by formulating capsules using the multiple-unit pellet system.

40 mg Nexium brand esomeprazole capsules

Multiple unit pellet system

Esomeprazole capsules are formulated as a "multiple unit pellet system" (MUPS). Essentially, the capsule consists of extremely small enteric-coated granules (pellets) of the esomeprazole formulation inside an outer shell. When the capsule is immersed in an aqueous solution, as happens when the capsule reaches the stomach, water enters the capsule by osmosis. The contents swell from water absorption causing the shell to burst, releasing the enteric-coated granules. For most patients, the multiple-unit pellet system is of no advantage over conventional enteric-coated preparations. Patients for which the formulation is of benefit include those requiring nasogastric tube feeding and those with difficulty swallowing (dysphagia).

The granules are manufactured in a fluid bed system with small sugar spheres as the starting material. The sugar spheres are sequentially spray-coated with a suspension containing esomeprazole, a protective layer to prevent degradation of the drug in manufacturing, an enteric coating and an outer layer to reduce granule aggregation. The granules are mixed with other inactive excipients and compressed into tablets. Finally, the tablets are film-coated to improve the stability and appearance of the preparation.

Side Effects

Common side effects include headache, diarrhea, nausea, gas, decreased appetite, constipation, dry mouth, and abdominal pain. More severe side effects are severe allergic reactions, chest pain, dark urine, fast heartbeat, fever, persistent sore throat, severe stomach pain, unusual bruising or bleeding, unusual tiredness, and yellowing of the eyes or skin.^[3]

Financial impact

Between the launch of esomeprazole in 2001 and 2005, the drug has netted AstraZeneca about $14.4 billion.^[4]

Controversy

There has been some controversy about AstraZeneca's behaviour in creating, patenting and marketing of the drug. Critics allege that the drug's successful predecessor Omeprazole is a mixture of two mirror-imaged molecules (esomeprazole and romeprazole), and that the company was trying to "evergreen" its patent by patenting the pure esomeprazole and aggressively marketing to doctors that it is more effective than the mixture,^[5] claiming that romeprazole has no beneficial effects on the patient. However, in the acidic environment of the parietal cells both esomeprazole and romeprazole are converted to the same active drug which stops the gastric acid production.

Dr. Marcia Angell, former Editor in Chief of the New England Journal of Medicine, spoke at Harvard Medical School to a German magazine on August 16, 2007 and accused AstraZeneca's scientists of deceptively doctoring their comparative studies such that the difference to Omeprazole would look larger, providing a marketing advantage.^[6] For more information, see AstraZeneca's article.

Thomas Scully, head of the Federal Centers for Medicare and Medicaid services also tore into Astra for their aggressive marketing of Nexium. At a conference of the American Medical Association he went so far as to suggest that Astra was using the new drug to overcharge consumers and insurance companies. "You should be embarrassed if you prescribe Nexium," he claimed, "because you're screwing your patients and you're screwing the taxpayers." An AstraZeneca sponsored study showed that esomeprazole 40 mg provided more effective acid control than 40 mg omeprazole.^[7]

Notes

Further reading

• Lind T, Rydberg L, Kylebäck A, et al. (July 2000). "Esomeprazole provides improved acid control vs. omeprazole In patients with symptoms of gastro-oesophageal reflux disease". Alimentary Pharmacology & Therapeutics 14 (7): 861–7. doi:10.1046/j.1365-2036.2000.00813.x. PMID 10886041. 

External links

• The official International Nexium website
• The official U.S. Nexium website