Omeprazole

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Abstract
Omeprazole is a well studied proton pump inhibitor that reduces gastric acid secretion. This review examines its use in Helicobacter pylori infection, gastrooesophageal reflux disease (GORD) with or without oesophagitis and gastrointestinal damage caused by nonsteroidal anti-inflammatory drugs (NSAIDs). Optimal omeprazole regimens for anti-H. pylori therapy are those that administer the drug at a dosage of 40 mg/day (in 1 or 2 divided doses) for 7, 10 or 14 days in combination with 2 antibacterial agents. As a component of 3-drug regimens in direct comparative studies, omeprazole was at least as effective as lansoprazole, pantoprazole, bismuth compounds and ranitidine. However, a meta-analysis suggests that triple therapies with omeprazole are more effective than comparable regimens containing ranitidine, lansoprazole or bismuth. Omeprazole also appears to be successful in triple therapy regimens used in children with H. pylori infection. In patients with acute GORD with oesophagitis, omeprazole is at least as effective as lansoprazole or pantoprazole in promoting healing, and superior to ranitidine, cimetidine or cisapride in oesophagitis healing and symptom relief. Omeprazole was similar to lansoprazole and superior to ranitidine in preventing oesophagitis relapse in patients with all grades of oesophagitis, but may be superior to lansoprazole or pantoprazole in patients with more severe disease. More patients with symptomatic GORD without oesophagitis experienced symptom relief after short term treatment with omeprazole than with ranitidine, cisapride or placebo, and symptoms were more readily prevented by omeprazole than by cimetidine or placebo. Omeprazole was effective in healing and relieving symptoms of reflux oesophagitis in children with oesophagitis refractory to histamine H2 receptor antagonists. Omeprazole is superior to placebo in preventing NSAID-induced gastrointestinal damage in patients who must continue to take NSAIDs. It is also similar to misoprostol and superior to ranitidine in its ability to heal NSAID-induced peptic ulcers and erosions, and superior to misoprostol, ranitidine or placebo in its ability to prevent relapse. In long and short term studies, omeprazole was well tolerated, with diarrhoea, headache, dizziness, flatulence, abdominal pain and constipation being the most commonly reported adverse events. Usual omeprazole dosages, alone or com-bined with other agents, are 10 to 40 mg/day for adults and 10 to 20 mg/day for children. Conclusions: Omeprazole is a well studied and well tolerated agent effective in adults or children as a component in regimens aimed at eradicating H. pylori infections or as monotherapy in the treatment and prophylaxis of GORD with or without oesophagitis or NSAID-induced gastrointestinal damage. Omeprazole inhibits the gastric parietal cell proton pump (H+/K+-ATPase), dose-dependently reducing basal and stimulated gastric acid secretion and raising intragastric pH. It works additively or synergistically with amoxicillin, clarithromycin and metronidazole in vitro against Helicobacter pylori. Absorption of omeprazole is unaffected by food and the drug is completely metabolised by cytochrome P450 enzymes and excreted in the urine and faeces. An analysis was conducted of pooled intention-to-treat data from 156 selected comparative and noncomparative clinical trials of omeprazole combined with antibacterials (with or without bismuth compounds) to eradicate H. pylori in more than 17 000 patients. Study design features such as randomisation, blinding and patient numbers had little effect on overall results. Triple therapy regimens containing omeprazole plus 2 antibacterial agents were the most effective regimens (median 86% eradication), followed by quadruple therapy (80%), triple therapy with omeprazole plus bismuth plus a single antibacterial agent (78%) and dual therapy (58%). Among the triple therapy regimens administering omeprazole plus 2 antibacterial agents, those administering omeprazole for 7 days (median 85% eradication), 10 days (91%) or 14 days (87%) were more effective than regimens of ≥4 weeks (81%) or all other durations (78%). Of the 7-, 10-or 14-day om-eprazole triple therapy regimens, optimal eradication rates were achieved by those administering omeprazole 40 mg/day in 1 or 2 divided doses (median 86 or 88% eradication); higher or lower dosages did not appear to offer additional therapeutic advantages. Commonly studied antibacterial combinations (amoxicillin/clarithromycin, clarithromycin, metronidazole, amoxicillin/metronidazole, clarithromycin/tinidazole) achieved high eradication rates as part of optimal omeprazole regimens. Current dosage recommendations are supportedby the results of our analysis. Results of this analysis are also in line with those of large clinical trials and meta-analyses. Omeprazole was at least as effective in achieving H. pylori eradication as lansoprazole, pantoprazole, ranitidine, ranitidine bismuth citrate or other bismuth compounds in comparative trials using these agents within 3-drug regimens. However, a meta-analysis suggests that triple therapy regimens containing omeprazole achieve consistently higher eradication rates than comparable triple therapy regimens containing histamine H2 receptor antagonists, lansoprazole or bismuth. Triple therapy regimens containing omeprazole also appear to be more cost effective than those containing bismuth or ranitidine. The addition of omeprazole to antibacterial drug regimens increased eradication rates to 67 to 94% (from 18 to 69% without omeprazole). In children with H. pylori infection, greater eradication rates were seen with a 3-drug omeprazole regimen than a 3-drug bismuth regimen. Eradication occurred in 68 to 93% of patients receiving 3-drug omeprazole regimens and 16 to 20% of recipients of 2-drug omeprazole regimens. Meta-analyses of short term studies in patients with gastro-oesophageal reflux disease (GORD) with oesophagitis suggest that omeprazole is superior in erosion-healing ability to H2 antagonists, cisapride, sucralfate and placebo. Individual short term (4-to 16-week) trials in patients with reflux oesophagitis show that healing occurred in similar proportions of patients receiving omeprazole 20 or 40 mg/day and those receiving either lansoprazole 30 mg/day or pantoprazole 40 mg/day, although omeprazole 20 mg/day was clearly superior to lansoprazole 15 mg/day in 1 trial. Nonerosive GORD healed as readily with ranitidine 150mg twice daily (with or without metoclopramide) as with omeprazole 20mg once daily, although erosive oesophagitis was more responsive to omeprazole 20mg once daily than ranitidine 150 or 300mg twice daily. The addition of cisapride 5mg 3 times daily to omeprazole 20mg once daily did not improve the short term healing of GORD. Omeprazole 20mg once daily provided superior relief of symp-toms of oesophagitis to ranitidine 300 mg/day, cisapride 40 mg/day or cimetidine 1600 mg/day after 4 weeks of treatment. Oesophagitis symptom relief was similar after omeprazole 20 mg/day, lansoprazole 15 or 30 mg/day or pantoprazole 40 mg/day, although lansoprazole 30 mg/day appeared to relieve symptoms more rapidly than omeprazole. A meta-analysis of long term (6-month) prophylaxis against reflux oesophagitis suggested that omeprazole 20 mg/day was more effective than omeprazole 10 mg/day, 20 mg/day at weekends, ranitidine 150mg twice daily or placebo. Individual 1-year studies also showed omeprazole 10 mg/day to be superior to placebo in preventing relapse, and omeprazole 20 mg/day with or without cisa-pride to be superior to ranitidine 150mg twice daily with or without cisapride. Although omeprazole 20 mg/day was similar to lansoprazole 15 or 30 mg/day in 1-year prophylaxis in patients with a range of grades of GORD, more studies are needed to determine if differences exist between proton pump inhibitors in patients with grade 4 disease. Redilatation was less likely to be required in patients with previous repeated dilatation of oesophageal strictures who received omeprazole 20 mg/day than in those receiving ranitidine 150mg twice daily. Omeprazole has also been shown to be effective in long term treatment of up to 11 years' duration. In patients with symptomatic GORD with or without oesophagitis, 4-to 8-week studies showed omeprazole 10 or 20mg once daily to be superior to ranitidine 150mg twice daily or cisapride 10mg 4 times daily in resolving symptoms. Longer term (6 month) studies indicate that dosages of omeprazole 10 or 20mg once daily were superior to cimetidine 800mg at bedtime or placebo in maintaining patients in a symptom-free state. Children with severe oesophageal reflux refractory to histamine H2 receptor antagonists appeared to respond well to omeprazole, although ongoing treatment with omeprazole 20 or 40 mg/day (depending on bodyweight) may be needed to maintain symptom relief. Omeprazole 20 mg/day was superior to placebo in a 6-month trial examining efficacy in the primary prevention of gastrointestinal damage induced by nonsteroidal anti-inflammatory drugs (NSAIDs) in patients who required ongoing NSAID therapy. Once NSAID-induced gastrointestinal damage had taken place, healing rates were similar in patients receiving omeprazole 20 or 40 mg/day or misoprostol 200µg 4 times daily for 4 to 8 weeks. Ranitidine 150mg twice daily, however, was less successful than omeprazole 20 or 40 mg/day in healing NSAID-induced peptic ulcers. In the secondary prevention of relapse of NSAID-induced gastrointestinal damage, omeprazole 20 mg/day was more successful than misoprostol 200µg twice daily, ranitidine 150mg twice daily or placebo in 6-month trials. Omeprazole is generally well tolerated, with most adverse events being mild, self-limiting and unrelated to dosage or patient age. Diarrhoea, flatulence, abdominal pain, constipation, headache and dizziness are among the more commonly reported events in short term trials. With long term omeprazole use, adverse events were generally consistent with those seen in short term trials. Omeprazole is similar in tolerability to lansoprazole, ranitidine and cimetidine, but appears to be better tolerated than bismuth compounds or misoprostol. For H. pylori eradication in adults, usual omeprazole dosages are 20mg twice daily or 40mg once daily for 7 or 10 days in combination with 2 antibacterial agents (clarithromycin plus either amoxicillin, metronidazole or tinidazole; or amoxicillin plus metronidazole) or 40 to 80 mg/day for 14 days with 1 antibacterial agent (amoxicillin or clarithromycin). Omeprazole 20mg once daily for 4 to 8 weeks is a usual dosage for healing of oesophagitis associated with GORD in adults; a higher 40 mg/day dosage and the full 8 weeks' treatment may be needed for more severe disease or in patients in whom healing does not occur after 4 weeks. To prevent oesophagitis relapse, omeprazole 10mg once daily is a usual dosage, but dosages of up to 40 mg/day may be used if needed. For symptomatic GORD, omeprazole 10 or 20mg once daily is used. In adult patients with NSAID-induced peptic ulcers, omeprazole 20mg once daily for 4 to 8 weeks is used for healing, and dosages of 20mg once daily are recommended to prevent relapse. Dosages of omeprazole for children with severe reflux oesophagitis are 10 mg/day (if 10 to 20kg in bodyweight) or 20 mg/day (>20kg). Omeprazole is not usually recommended for use during pregnancy or breast feeding. Its dosages do not require adjustment in elderly patients or those with renal impairment. A dosage of 10 or 20 mg/day is usually sufficient for patients with hepatic impairment. Plasma levels of warfarin, phenytoin or digoxin should be monitored if omeprazole is added to regimens of these drugs.