OMEPRAZOLE - AN UPDATE OF ITS PHARMACOLOGY AND THERAPEUTIC USE IN ACID-RELATED DISORDERS

Omeprazole, a gastric acid pump inhibitor dose-dependently controls gastric acid secretion; the drug has greater antisecretory activity than histamine H-2-receptors antagonists Omeprazole 20 to 40 mg/day is more effective than histamine H-2-receptor antagonists in the short term treatment of duodenal ulcer, gastric ulcer and reflux oesophagitis. Available data suggest that omeprazole 10 to 40 mg/day is also more effective than ranitidine in the maintenance therapy of duodenal ulcer and reflux oesophagitis. The drug is also effective in patients with duodenal ulcer, gastric ulcer or reflux oesophagitis poorly responsive to histamine H-2-receptor antagonists. The efficacy of omeprazole 20 mg/day appears to be similar to that of lansoprazole 30 mg/day in the short term treatment of duodenal ulcer, gastric ulcer and reflux oesophagitis. However, most available studies have been reported in abstract form only, and 2 of 3 studies in patients with duodenal ulcer have shown greater healing rates at 2 (but not 4) weeks with lansoprazole. Helicobacter pylori eradication decreases duodenal ulcer relapse rates and appears to be associated with improved duodenal ulcer healing rates. Evidence also suggests that H. pylori eradication is associated with reduced gastric ulcer relapse rates. Omeprazole monotherapy may suppress but does not eradicate H. pylori infection. Eradication rates with omeprazole 20 or 40mg twice daily plus amoxicillin usually up to 2 g/day (3 g/day in a few studies) for 2 weeks appear to be similar to those of standard triple therapy (bismuth salt plus metronidazole, plus tetracycline or amoxicillin) or omeprazole plus clarithromycin, although eradication rates vary widely. Omeprazole plus amoxicillin appears to be better tolerated than triple therapy and represents a first-line treatment alternative in patients with H. pylori-associated peptic ulcer disease. Omeprazole plus amoxicillin plus metronidazole appears to be more effective than omeprazole plus amoxicillin in patients with metronidazole-sensitive H. pylori infection. Omeprazole remains a treatment of choice in patients with Zollinger-Ellison syndrome. The dosage should be adjusted according to individual response. However, relatively low dosages of 10 to 40 mg/day may be sufficient in some patients. The drug has also shown promise in the treatment of children with severe reflux oesophagitis, in patients with reflux oesophagitis and coexisting systemic sclerosis, and in the prevention of aspiration pneumonia. Evidence suggests that omeprazole is more effective than ranitidine in patients with nonsteroidal anti-inflammatory drug (NSAID)-induced gastric damage who continue to take NSAIDs, especially in patients with large gastric ulcers; however, completion of ongoing studies is required to verify this. Omeprazole is generally well tolerated during short (<12 weeks) and long (up to 10 years or more) term treatment. The most common, albeit infrequent, adverse effects are gastrointestinal in nature and are similar to those with histamine H-2-receptor antagonists. Thus, omeprazole is a first-line agent in the short and long term treatment of reflux oesophagitis, Zollinger-Ellison syndrome, and the short and long term treatment of peptic ulcer disease. Omeprazole plus amoxicillin appears to be of similar efficacy to, and better tolerated than, bismuth-containing triple therapy in eradicating H. pylori infection. Simultaneous ulcer healing, symptom resolution and H. pylori eradication is likely to become the management strategy of choice in H. pylori-positive duodenal ulcer disease, with omeprazole poised to play a substantial role in such therapy.