Omeprazole. An update of its pharmacology and therapeutic use in acid-related disorders

Helicobacter pylori: rational management options

In the treatment of Helicobacter pylori-associated peptic ulcer disease, the complexity (ie, frequency and duration) of drug administration, the presence or development of bacterial antibiotic resistance, and the occurrence of side effects influence patient compliance and eradication rates, which consequently affect the costs of treatment regimens. The National Institutes of Health Consensus Conference and 1997 Digestive Health Initiative Update Conference have recommended that all patients with gastric or duodenal ulcer and H. pylori infection, whether on first presentation or recurrence, be treated with antimicrobials. However, H. pylori resistance to antimicrobials, specifically to nitroimidazole compounds, has resulted in varied and decreasing success rates of treatment regimens. Comparing the efficacy, safety, and costs of current treatment strategies for the eradication of H. pylori, a combination triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin is recommended as an effective alternative to standard bismuth-based triple therapy. When compared with other therapies, these offer more rapid symptomatic relief, improved tolerability, increased compliance and efficacy, and moderate costs.

Omeprazole. A review of its use in Helicobacter pylori infection, gastro-oesophageal reflux disease and peptic ulcers induced by nonsteroidal anti-inflammatory drugs

Omeprazole is a well studied proton pump inhibitor that reduces gastric acid secretion. This review examines its use in Helicobacter pylori infection, gastro-oesophageal 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 combined 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.

Proton pump inhibitors. Pharmacology and rationale for use in gastrointestinal disorders

Proton pump inhibitors (PPIs) are drugs which irreversibly inhibit proton pump (H+/K+ ATPase) function and are the most potent gastric acid-suppressing agents in clinical use. There is now a substantial body of evidence showing improved efficacy of PPIs over the histamine H2 receptor antagonists and other drugs in acid-related disorders. Omeprazole 20 mg/day, lansoprazole 30 mg/day, pantoprazole 40 mg/day or rabeprazole 20 mg/day for 2 to 4 weeks are more effective than standard doses of H2-receptor antagonists in healing duodenal and gastric ulcers. Patients with gastric ulcers should receive standard doses of PPIs as for duodenal ulcers but for a longer time period (4 to 8 weeks). There is no conclusive evidence to support the use of a particular PPI over another for either duodenal or gastric ulcer healing. For Helicobacter pylori-positive duodenal ulceration, a combination of a PPI and 2 antibacterials will eradicate H. pylori in over 90% of cases and significantly reduce ulcer recurrence. Patients with H. pylori-positive gastric ulcers should be managed similarly. PPIs also have efficacy advantages over ranitidine and misoprostol and are better tolerated than misoprostol in patients taking nonsteroidal anti-inflammatory drugs (NSAIDs). In endoscopically proven gastro-oesophageal reflux disease, standard daily doses of the PPIs are more effective than H2-receptor antagonists for healing, and patients should receive a 4 to 8 week course of treatment. For severe reflux, with ulceration and/or stricture formation, a higher dose regimen (omeprazole 40 mg, lansoprazole 60 mg, pantoprazole 80 mg or rabeprazole 40 mg daily) appears to yield better healing rates. There is little evidence that PPIs lead to resolution of Barrett's oesophagus or a reduction of subsequent adenocarcinoma development, but PPIs are indicated in healing of any associated ulceration. In Zollinger-Ellison syndrome, PPIs have become the treatment of choice for the management of gastric acid hypersecretion.

A Comparison of Retrospective and Concurrent Drug Utilization Review of Omeprazole

Objective:

To compare the appropriateness of omeprazole prescriptions in a concurrent drug utilization review (DUR) with the assessed appropriateness of a retrospective DUR.

Methods:

A retrospective DUR of omeprazole was conducted on prescriptions written from August 23, 1993, to October 8, 1993, in a 340-bed university hospital. This DUR served as a baseline for a concurrent DUR that began on January 27, 1995, and ended on March 16, 1995. The concurrent DUR integrated three steps aimed at improving the quality of omeprazole use: Approval of the criteria by the pharmacology and therapeutics committee of the hospital, distribution of a drug bulletin to all physicians, and a pharmacist's verbal recommendations to physicians whose prescriptions did not meet explicit criteria.

Results:

Twenty-nine and 64 prescriptions were reviewed in the retrospective and concurrent DURs, respectively. During the concurrent DUR, the pharmacist made 34 verbal recommendations. Of these, 25 (74%) were agreed to by the prescribers. In comparison with the retrospective DUR, the percentage of prescriptions meeting the criteria of indication, combination therapy, and dosage went from 38% to 75% (p < 0.05), from 76% to 95% (p < 0.05), and from 83% to 100% (p > 0.05), respectively, during the concurrent DUR.

Conclusions:

The concurrent DUR appeared to successfully improve the quality of omeprazole utilization in the hospital.

A prospective randomized trial comparing the use of omeprazole-based dual and triple therapy for eradication of Helicobacter pylori

BACKGROUND

Controversy surrounds the optimal composition, dosage, and duration of therapies for eradication of Helicobacter pylori. We prospectively compared omeprazole-based dual and triple therapies in the eradication of H. pylori in a randomized manner.

METHODS

Between June 1995 and March 1997, 1000 consecutive patients with acid-peptic disease associated with H. pylori infection (duodenal ulcer, 388 patients, gastric ulcer, 179 patients; duodenitis, 173 patients; gastritis, 260 patients) were prospectively recruited. They were randomized to either a 2-wk (OA) course of omeprazole 20 mg and amoxicillin 1 g, both given twice daily, or treatment for 1 wk (OCM) with omeprazole 20 mg once daily, clarithromycin 500 mg twice daily, and metronidazole 400 mg twice daily.

RESULTS

The age of these 1000 patients ranged from 16 to 90 yr, with a mean of 54.9 yr. Side effects occurred in 29.6% (95% confidence interval [CI] 25.6-33.8%) and 10.6% (95% CI 8.0-13.6%) of patients taking OCM and OA, respectively (p < 0.0001). Apart from taste disturbance, however, there were no significant differences in the incidences of side effects between the two groups. One patient in the OA group and four patients of the OCM group could not tolerate the medications, and therefore did not complete treatment (p = 0.37). Seven and 13 patients in the OA and OCM groups, respectively, refused a second endoscopy (p = 0.25). The remaining 975 patients underwent a second endoscopy. Positive endoscopic findings were significantly more common in the OA group (51/492; 10.4%; 95% CI 7.8-13.4%) than in the OCM group (25/483; 5.2%; 95% CI 3.4-7.5%) in the per-protocol (PP) analysis (p = 0.004). On intent-to-treat (ITT) analysis, the overall eradication rates in the OA and OCM groups were 73.6% (95% CI 69.5-77.4%) and 92% (95% CI 89.3-94.2%), respectively (p < 0.0001). On PP analysis, the corresponding rates were 74.8% (95% CI 70.7-78.6%) and 95.2% (95% CI 92.9-97.0%), respectively (p < 0.0001).

CONCLUSIONS

A course of omeprazole, clarithromycin, and metronidazole for 1 wk is a safe, well-tolerated, efficacious, and cost-effective treatment for H. pylori infection.

Omeprazole and ranitidine in long-term treatment of duodenal ulcer: a double-blind comparison of length of time in remission

In most patients duodenal ulcer is a chronic relapsing disease. If no active maintenance treatment or eradication therapy is given after healing, around 70-100% of patients have a relapse during the first year. We conducted a double-blind multicenter study in 472 patients with duodenal ulcer. They were treated with omeprazole 20 mg every morning for four or eight weeks and when healed were randomly allocated to maintenance treatment with either omeprazole 20 mg every morning or ranitidine 150 mg at bedtime for up to six months. The patients were assessed by endoscopy at monthly intervals until healing occurred. Thereafter scheduled endoscopy was carried out after 1, 3, and 6 months of maintenance treatment or immediately in the event of a suspected relapse. Healing status (intention to treat approach) was 87% at four weeks and 93% at eight weeks. At six months the estimated remission rate was 90% for omeprazole and 82% for ranitidine (P = 0.03, 95% CI 1-15%). The incidence of adverse events was similar during the two maintenance treatments. Treatment with omeprazole 20 mg every morning maintained significantly more patients in remission than treatment with ranitidine 150 mg at bedtime.

Effect of long-term gastric acid suppressive therapy on serum vitamin B12 levels in patients with Zollinger-Ellison syndrome

BACKGROUND AND AIMS

Long-term treatment with H(+)-K(+)-adenotriphosphatase (ATPase) inhibitors, such as omeprazole or lansoprazole, for severe gastroesophageal reflux disease is now widely used. Whether such treatment will result in vitamin B12 deficiency is controversial. We studied whether long-term treatment with omeprazole alters serum vitamin B12 levels in patients with Zollinger-Ellison syndrome.

METHODS

In 131 consecutive patients treated with either omeprazole (n = 111) or histamine H2-receptor antagonists (n = 20), serum vitamin B12 and folate levels and complete blood counts were determined after acid secretion had been controlled for at least 6 months. These studies were repeated yearly. Serum vitamin B12 and folate levels were correlated with the type of antisecretory drug and the extent of inhibition of acid secretion.

RESULTS

The mean duration of omeprazole treatment was 4.5 years, and for H2-receptor antagonists 10 years. Vitamin B12 levels, but not serum folate levels or any hematological parameter, were significantly (P = 0.03) lower in patients treated with omeprazole, especially those with omeprazole-induced sustained hyposecretion (P = 0.0014) or complete achlorhydria (P < 0.0001). In 68 patients with two determinations at least 5 years apart, vitamin B12 levels decreased significantly (30%; P = 0.001) only in patients rendered achlorhydric. The duration of omeprazole treatment was inversely correlated with vitamin B12 levels (P = 0.013), but not folate levels. Eight patients (6%) developed subnormal B12 levels during follow-up.

CONCLUSIONS

Long-term omeprazole treatment leads to significant decreases in serum vitamin B12 but not folate levels. These results suggest patients with Zollinger-Ellison syndrome treated with H(+)-K(+)-ATPase inhibitors should have serum vitamin B12 levels monitored. Furthermore, these results raise the possibility that other patients treated chronically with H(+)-K(+)-ATPase inhibitors may develop B12 deficiency.

In vitro activity of ebrotidine, ranitidine, omeprazole, lansoprazole, and bismuth citrate against clinical isolates of Helicobacter pylori

The aim of this study was to determine the in vitro activity of ranitidine, ebrotidine, bismuth citrate, omeprazole, and lansoprazole against 113 clinical isolates of Helicobacter pylori cultured from gastric biopsies. An agar dilution method using Mueller-Hinton agar plus 7%, horse blood, an inoculum of 10(6) cfu/spot, and incubation in a CO2 incubator for 2 to 5 days was used. The minimum inhibitory concentrations for 50 and 90% of the isolates tested, respectively, were as follows: ranitidine, 1024 and 1024 mg/l; ebrotidine, 64 and 256 mg/l; bismuth citrate, 1 and 4 mg/l; omeprazole, 16 and 16 mg/l; and lansoprazole, 1 and 1 mg/l. Ebrotidine was more active than ranitidine, and lansoprazole was the most active compound against the Helicobacter pylori isolates tested.

Pharmacokinetics of drugs used in critically ill adults

Critically ill patients exhibit a range of organ dysfunctions and often require treatment with a variety of drugs including sedatives, analgesics, neuromuscular blockers, antimicrobials, inotropes and gastric acid suppressants. Understanding how organ dysfunction can alter the pharmacokinetics of drugs is a vital aspect of therapy in this patient group. Many drugs will need to be given intravenously because of gastrointestinal failure. For those occasions on which the oral route is possible, bioavailability may be altered by hypomotility, changes in gastrointestinal pH and enteral feeding. Hepatic and renal dysfunction are the primary determinants of drug clearance, and hence of steady-state drug concentrations, and of efficacy and toxicity in the individual patient. Oxidative metabolism is the main clearance mechanism for many drugs and there is increasing recognition of the importance of decreased activity of the hepatic cytochrome P450 system in critically ill patients. Renal failure is equally important with both filtration and secretion clearance mechanisms being required for the removal of parent drugs and their active metabolites. Changes in the steady-state volume of distribution are often secondary to renal failure and may lower the effective drug concentrations in the body. Failure of the central nervous system, muscle, the endothelial system and endocrine system may also affect the pharmacokinetics of specific drugs. Time-dependency of alterations in pharmacokinetic parameters is well documented for some drugs. Understanding the underlying pathophysiology in the critically ill and applying pharmacokinetic principles in selection of drug and dose regimen is, therefore, crucial to optimising the pharmacodynamic response and outcome.

[Risk of ulcer and its prophylaxis in therapy with non-steroidal antirheumatic drugs]

Nonsteroidal antiinflammatory drugs (NSAIDs) are among the most frequently prescribed drugs in western countries. The high incidence of adverse gastrointestinal effects which are potentially life-threatening require steps for prevention. The use of NSAIDs should be restricted to patients with inflammatory rheumatic diseases. If NSAIDs are indicated it is important to identify patients who are at high risk to develop serious gastrointestinal side effects. These patients should receive Misoprostol at a dose of 2 to 3 x 200 micrograms per day. Up to date Misoprostol is the only drug with proven efficacy with respect to the prevention of gastroduodenal ulcer and its complications. NSAIDs inhibit the key enzyme of prostaglandin synthesis, the cyclooxygenase. Recently published data show that 2 isoenzymes of the cyclooxygenase exists. Cyclooxygenase-1 is primarily involved in the maintenance of organ function whereas cyclooxygenase-2 is expressed in inflamed tissue. Specific cyclooxygease-2 inhibitors have been developed. Clinical trials have to prove if the concept of a selective cyclooxygenase-2 inhibition with high antiinflammatory potency but lack of gastrointestinal side effects holds true in humans.

The efficacy of benzimidazole drugs against Plasmodium falciparum in vitro

The sensitivities in vitro of Plasmodium falciparum to the benzimidazoles, albendazole, thiabendazole, mebendazole, omeprazole and 2 albendazole metabolites, albendazole sulphone and albendazole sulphoxide, were investigated and compared to those of the commonly used antimalarial drugs chloroquine and quinine. Quinine and chloroquine were the most potent drugs tested (EC50 values of 8 x 10(-9)-6 x 10(-8) mol/L and 5-7 x 10(-9) mol/L, respectively). Thiabendazole, mebendazole, albendazole sulphone and albendazole sulphoxide reached maximum growth inhibitions of 13-36% at the highest concentration tested (1 x 10(-4) mol/L). Albendazole (EC50 range: not achieved-2 x 10(-6) mol/L) and omeprazole (EC50 range: 2-4 x 10(-5) mol/L) were the most effective benzimidazoles. The activity of albendazole was pH dependent, as was that of chloroquine, and variable. Albendazole has its primary mode of action on trophozoites, suggesting that the drug may target parasite tubulin polymerization. Omeprazole, although also primarily effective against trophozoites, had additional activity against schizonts and ring forms, suggesting a distinct or additional parasitic target. Given the variable activity of albendazole and its rapid metabolism in vivo into compounds with even less antimalarial activity, it appears unlikely that this benzimidazole will be useful in the treatment of malaria. The rapid activity and different stage-specific profile of the more soluble benzimidazole omeprazole warrants further investigation.

Twenty-four-hour intragastric acidity and plasma gastrin during 3-month treatment with omeprazole in healthy subjects

BACKGROUND

Prolonged treatment with omeprazole 20 or 40 mg/day is sometimes required, especially for severe oesophagitis. However, information about long-term effects on intragastric acidity and plasma gastrin response with such drug regimens is scarce.

METHODS

Sixteen healthy subjects (11 men, 5 women, mean age 29 years) randomly received either 20 or 40 mg of omeprazole once daily (at 08.00 h) for 3 months. Gastric pH was recorded every 6 s for 24 h from noon to noon under standardized conditions, and blood samples were collected hourly in order to determine the 24-h plasma gastrin response on day 0 (pre-entry), day 7, day 28 and day 90.

RESULTS

From day 0 to day 7, 24-h median pH increased from 1.7 to 4.6 and mean percentage of time at pH < 4 decreased from 89% to 35% with omeprazole 20 mg. Respective values with omeprazole 40 mg were 1.9 to 4.3, and 89% to 34%. Inhibition of gastric acidity remained unchanged during the 3 months of treatment. Despite similar effects on the basis of 24-h analysis, the decrease in daytime acidity was slightly higher with omeprazole 40 mg than with omeprazole 20 mg. Twenty-four-hour integrated plasma gastrin significantly increased with both drug regimens between day 0 and day 7 (P < 0.01), and between day 7 and day 28 (P < 0.01) with omeprazole 40 mg; there was no significant increase between day 28 and day 90 with either of the drug regimens.

CONCLUSION

Omeprazole 20 and 40 mg/day provides long-term stable acid suppression with a progressive increase in gastrin response, stabilizing after 2 months of treatment.

Determination of omeprazole in human plasma by high-performance liquid chromatography

A new method for the determination of omeprazole in human plasma was developed. Omeprazole was extracted from plasma with toluene-isoamylalcohol (95:5, v/v), the organic phase was evaporated, dissolved in the mobile phase and injected into a reversed-phase C18 column. Flunitrazepam was used as an internal standard. The mobile phase consisted of 47% methanol and 53% of 0.1 M dipotassium hydrogenphosphate, pH 7.8. The spectrophotometric detection was performed at 302 nm. Limit of quantitation was 9.7 ng/ml and the calibration curve was linear up to 1240 ng/ml.

Use of Intravenous Omeprazole in a University Hospital

Objective:

To evaluate the characteristics of using intravenous omeprazole in a university hospital.

Method:

A prospective follow-up of all patients (n = 108) treated with intravenous omeprazole in our hospital was done from October 1994 through May 1995. Based on requests sent to the pharmacy service, patients receiving this drug were located and their charts were reviewed. The patients were visited daily throughout the duration of their treatment to evaluate any change in dosage, addition of new drugs to the regimen, and the final date of treatment.

Results:

Only 52% of the patients received omeprazole for indications in which its usefulness is clearly demonstrated. The dosages used frequently exceeded those recommended by the pharmaceutical manufacturer and in the literature. In fact, more than 50% of the patients were treated with dosages over 40 mg/d. It would have been possible to administer omeprazole orally instead of intravenously in 17% of the patients. Twenty-three percent of the patients were treated simultaneously with omeprazole and histamine2-antagonists.

Conclusions:

The use of intravenous omeprazole in our hospital is not optimal; thus, it seems that a strategy to improve this situation should be designed.

Respiratory complications of gastroesophageal reflux disease

There is a relationship between gastroesophageal reflux disease and certain respiratory symptoms and findings. Among these are cough, laryngitis, and wheezing dyspnea. The pathophysiology of these conditions can vary from actual aspiration of gastric content to esophageal mucosal inflammation with the respiratory symptoms induced by a vagally mediated reflex mechanism.

A risk-benefit assessment of drugs used in the eradication of Helicobacter pylori infection

Helicobacter pylori is the cause of chronic active gastritis and predisposes to peptic ulcer disease (PUD). Furthermore, H. pylori is linked to the pathogenesis of gastric lymphoma and gastric cancer. However, treatment of this infection has proven difficult. In the last decade, many antimicrobial compounds have been studied extensively as monotherapy as well as in combination with bismuth or acid-suppressive drugs. The individual drugs and the most important eradication regimens are discussed with special regard to their risks. In the past, highly complex multidrug regimens, fear of adverse effects and frequent eradication failures have hampered the broad acceptance of H. pylori-eradication therapies. Recently, new 1-week, low-dose combination regimens of 2 antibacterials with a proton pump inhibitor have consistently achieved eradication rates of 90% and more with an acceptably low rate of adverse effects. One week's standard triple therapy [tripotassium dicitrato bismuthate (or bismuth salicylate plus metronidazole plus tetracycline or amoxicillin) has been shown to be highly effective and tolerated better in combination with a proton pump inhibitor. This regimen is, however, more complex and has more adverse effects. Therefore, it is not recommended as first-line therapy. Equipped with these therapies physicians can now be strongly encouraged to use H. pylori eradication as the therapy of choice for patients with PUD and even extend this treatment to other H. pylori-associated disease conditions.

Pantoprazole. A review of its pharmacological properties and therapeutic use in acid-related disorders

Pantoprazole is an irreversible proton pump inhibitor which, at the therapeutic dose of 40mg, effectively reduces gastric acid secretion. In controlled clinical trials, pantoprazole (40mg once daily) has proved superior to ranitidine (300mg once daily or 150mg twice daily) and equivalent to omeprazole (20mg once daily) in the short term (< or = 8 weeks) treatment of acute peptic ulcer and reflux oesophagitis. Gastric and duodenal ulcer healing proceeded significantly faster with pantoprazole than with ranitidine, and at similar rates with pantoprazole and omeprazole. The time course of gastric ulcer pain relief was similar with pantoprazole, ranitidine and omeprazole, whereas duodenal ulcer pain was alleviated more rapidly with pantoprazole than ranitidine. Pantoprazole (40mg once daily) showed superior efficacy to famotidine (40mg once daily) in ulcer healing and pain relief after 2 weeks in patients with duodenal ulcer in a large multicentre nonblinded study. In mild to moderate acute reflux oesophagitis, significantly greater healing was obtained with pantoprazole than with ranitidine and famotidine, whereas similar healing rates were seen with pantoprazole and omeprazole. Pantoprazole showed a significant advantage over ranitidine in relieving symptoms of heartburn and acid regurgitation. Reflux symptoms were similarly alleviated by pantoprazole and omeprazole. Preliminary results indicate that triple therapy with pantoprazole, clarithromycin and either metronidazole or tinidazole is effective in the treatment of Helicobacter pylori-associated disease; however, these findings require confirmation in large well-controlled studies. Pantoprazole appears to be well tolerated during short term oral administration, with diarrhoea (1.5%), headache (1.3%), dizziness (0.7%), pruritus (0.5%) and skin rash (0.4%) representing the most frequent adverse events. The drug has lower affinity than omeprazole or lansoprazole for hepatic cytochrome P450 and shows no clinically relevant pharmacokinetic or pharmacodynamic interactions at therapeutic doses with a wide range of drug substrates for this isoenzyme system. In conclusion, pantoprazole is superior to ranitidine and as effective as omeprazole in the short term treatment of peptic ulcer and reflux oesophagitis, has shown efficacy when combined with antibacterial agents in H. pylori eradication, is apparently well tolerated and offers the potential advantage of minimal risk of drug interaction.

A prospective study of the effectiveness of low dose omeprazole as initial therapy in Zollinger-Ellison syndrome

BACKGROUND

The proton pump inhibitors (omeprazole and lansoprazole) are the drugs of choice for the medical management of gastric acid hypersecretion in Zollinger-Ellison syndrome (ZES). These drugs are safe for long-term therapy but are acid-labile and high doses are expensive. The recommended starting dose of omeprazole is 60 mg/day. However, it has been shown in recent studies that the maintenance dose of omeprazole could be safely reduced to 20 mg once or twice a day in more than two-thirds of patients with ZES. The purpose of this study is to determine if an initial starting dose of omeprazole 20 mg/day is safe and effective in patients with ZES.

METHODS

Forty-nine consecutive patients with ZES being treated with ranitidine for at least 2 weeks were admitted to the NIH. Omeprazole 20 mg was started on day 1 of the admission and ranitidine discontinued 4 h after the first dose. Gastric acid output was measured for 1 h prior to the next omeprazole dose on day 2, then on day 3 if the value was > 10 mmol/h on the previous day. If acid-peptic symptoms developed or the gastric acid output remained > 10 mmol/h on day 3, the patient was considered to have failed omeprazole 20 mg/day initial therapy and the dose titrated daily to achieve adequate control of acid-peptic symptoms and gastric secretion.

RESULTS

In 33 of the 49 patients (68%) omeprazole 20 mg/day was successful as initial therapy. Sixteen patients (32%) failed this initial omeprazole dose (eight patients owing to persistent peptic symptoms and eight patients owing to inadequate acid control). The final daily omeprazole dose required in these patients was 40 mg in eight patients (16%), 60 mg in one patient (2%) and 80 mg in seven patients (14%). Basal acid output (BAO) was the only clinical or laboratory feature that was significantly different between the two groups in which low dose initial omeprazole therapy was or was not successful; all patients with basal acid output < 20 mmol/h had a successful outcome.

CONCLUSIONS

Because of the need to rapidly control gastric acid hypersecretion owing to the high risk of complications from peptic ulcer disease, patients with ZES should continue to be started on omeprazole 60 mg/day and the dose adjusted by acute titration methods as is currently recommended. After a maintenance dose is established, attempts should be undertaken to reduce the dose to 20 mg/ day once or twice a day. Only the minority of patients with ZES in whom basal acid output is known to be < 20 mmol/h (20% of patients) should be started on a low initial omeprazole dose.

Clarithromycin and omeprazole as helicobacter pylori eradication therapy in patients with H. pylori-associated gastric disorders

Helicobacter pylori is susceptible to many antibacterial drugs in vitro but has proved difficult to eradicate in vivo. The macrolide clarithromycin has good activity against H. pylori in vitro and has demonstrated the highest eradication rate for any antibacterial monotherapy in vivo. However, it is clear that antibacterial monotherapy is not a sufficiently effective treatment for patients with H. pylori infection. The suggestion that high intragastric acidity impairs the action of antibacterial drugs led to the evaluation of combination H. pylori eradication regimens including H+,K+-ATPase inhibitors and antibacterial drug(s) with or without bismuth compounds. Noncomparative studies evaluating the efficacy of dual therapy with clarithromycin plus omeprazole in patients with H. pylori infection have reported eradication rates of between 58 and 83% > or = 4-weeks after therapy. In comparative studies, clarithromycin plus omeprazole was at least as effective as amoxicillin plus omeprazole. However, direct comparisons have shown that eradication rates achieved by dual therapy are not as high as those achieved by triple therapy. Indeed, triple therapy with clarithromycin plus omeprazole in combination with amoxicillin or a nitroimidazole has achieved eradication rates of up to 100%. Although 14-day triple drug regimes were initially considered necessary for effective eradication, it now seems clear that 7-day regimes are equally effective. Factors known to influence response to H. pylori eradication therapy include bacterial resistance and patient compliance. A review of 4 studies evaluating the efficacy of dual eradication therapy with clarithromycin plus omeprazole reported an overall incidence of adverse events (patient or investigator reported, whether related to treatment or not) of 45%. The most common adverse event was taste disturbance (an adverse event commonly reported during the development of clarithromycin); nausea, headache, diarrhoea, vomiting and abdominal pain occurred less frequently. Although dual therapy might be expected to cause fewer adverse events than triple therapy this has not been the case in direct comparisons conducted to date. Thus, although clarithromycin plus omeprazole is associated with an H. pylori eradication rate of approximately 70%, 1 week of triple therapy with these 2 drugs together with amoxicillin or a nitroimidazole, which eradicates the organism in approximately 90% of cases, may represent optimal H. pylori eradication therapy.

Pharmacokinetic optimisation of the treatment of peptic ulcer in patients with renal failure

The pathogenesis of peptic ulceration is not yet clear. It could be due to an imbalance between acid secretion and mucosal defensive and/or protective mechanisms, but the association between Helicobacter pylori and peptic ulceration has questioned this hypothesis. Therefore, drugs inhibiting acid secretion and/or eradicating H. pylori are of major interest. Peptic ulcer disease is often associated with renal failure. For the selection of the proper dosage of these agents their pharmacokinetic properties and alterations in pharmacokinetics in various disease states, including renal failure, should be known. As histamine H2-receptor antagonists and pirenzepine are mainly eliminated by the renal route their elimination is dependent on creatinine clearance. Consequently, their elimination will be impaired in patients with renal insufficiency, which makes dosage reduction mandatory in these patients. No dosage supplementation is necessary after any type of dialysis because the drugs are removed in insignificant amounts by the various blood purification procedures. Misoprostol and proton pump inhibitors, such as omeprazole, lansoprazole and pantoprazole, are primarily eliminated by nonrenal routes. Therefore no dosage adjustments are necessary in patients with renal insufficiency. Bismuth salts, sucralfate and antacids should be avoided in patients with renal failure because of the accumulation of their cations and the associated risk of toxic reactions. For most agents more long term experience from comparative and double-blinded studies is needed to define better their clinical efficacy and tolerability in patients with renal failure.