Omeprazole

Lansoprazole in children: pharmacokinetics and efficacy in reflux oesophagitis

BACKGROUND

Data on the proton pump inhibitor lansoprazole in paediatric patients are limited.

AIM

To investigate the pharmacokinetics, optimal dosage and efficacy of lansoprazole in paediatric patients.

METHODS

A 24-h gastric pH recording and a pharmacokinetic study were performed after 7 days of lansoprazole, 17 mg/m2, in 23 patients with reflux oesophagitis (median age, 3.5 years). Response was defined as pH > 3 for > 65% of the recording. The dosage was doubled in non-responders. Patients with no response on day 14 were excluded. Responders underwent endoscopy after 4 weeks on the response-inducing dosage; abnormal findings led to a repeat endoscopy after four additional weeks.

RESULTS

Nine patients responded to 17 mg/m2 and six to 30.3 mg/m2. On day 7, time with pH > 3 was significantly correlated with the area under the plasma concentration-time curve (P=0.003). The area under the plasma concentration-time curve was significantly greater in the nine responders to 17 mg/m2 than in the 14 other patients. Pharmacokinetic parameters were similar in responders and non-responders to the higher dose. After 4 weeks, oesophagitis was healed in 80% of responders. Adverse events occurred in three patients and required treatment discontinuation in one.

CONCLUSIONS

Lansoprazole is effective and safe in children. The optimal starting dosage is 30 mg/m2 or 1.4 mg/kg.

Intravenous omeprazole in children: pharmacokinetics and effect on 24-hour intragastric pH

BACKGROUND

Omeprazole is a proton pump inhibitor, acting selectively on the gastric parietal cell H+K+-adenosine triphosphatase. Data on the intravenous route are limited in children and not available in infants.

OBJECTIVE

This study was designed to determine the pharmacokinetics and the optimal dosage of intravenous omeprazole in patients younger than 30 months of age.

METHODS

Nine children (three girls), aged 4.5 to 27 months, with normal liver and renal functions requiring intravenous omeprazole were studied. After enrollment in the study and randomization, omeprazole was administered once daily, at 8 am, as a 1-hour infusion. Group 1, consisting of the first four patients, received 20 mg/1.73 m2, and group 2, consisting of the following five patients, received 40 mg/1.73 m2. At day 3, a 24-hour intragastric pH and a pharmacokinetic study of omeprazole were performed. Plasma concentrations were measured by high-performance liquid chromatography.

RESULTS

Patients in group 2 had a significantly higher median pH (6.99 vs. 3.35; P = 0.01) and percent of monitored time with gastric pH >4 than children given 20 mg/1.73 m2 (90.6% vs. 44.8%; P < 0.01). Four had a pH more than 4 during more than 90% of the time versus none of the patients of group 1. The plasma concentration versus time curves showed rapid elimination of the drug. The median area under the curve of omeprazole was 0.78 microg. mL-1. h-1 (range, 0.55-1.64 microg. mL-1. h-1) and 3.95 microg. mL-1. h-1 (range, 1.9-4.9 microg. mL-1. h-1), respectively, in groups 1 and 2 (P < 0.05). Systemic clearance was not different between the two groups: median values were 0.68 and 0.42 L. kg-1. h-1 (P = 0.22).

CONCLUSIONS

In critical situations, intravenous administration of omeprazole may be required in infants. The authors demonstrate that the dose of 20 mg/1.73 m2 is not effective in maintaining 24-hour gastric pH of more than 4 and that a dose of 40 mg/1.73 m2 is required.

Effect of long-term, continuous versus alternate-day omeprazole therapy on serum gastrin in patients treated for reflux esophagitis

BACKGROUND

Proton pump inhibitors have been proven to have a major role in the management of peptic diseases, especially the long-term control of reflux esophagitis. The potent inhibitory effect of omeprazole on gastric acid secretion is frequently associated with hypergastrinemia, and gastrin and its intermediates have been reported to promote gastrointestinal cellular functions and cell growth. Experimental data suggest that gastrin may affect the proliferation of colon cells and some other cancer cells. However, so far the direct role of gastrin in tumorigenesis is unclear. Although most clinical studies on long-term treatment with omeprazole or other proton pump inhibitors do not report serious adverse effects, the issue of prolonged hypergastrinemia and tissue growth is unsettled, and many clinicians are reluctant to recommend long-term use of omeprazole or of other proton pump inhibitors.

STUDY

We examined the effect of long-term omeprazole treatment on serum gastrin levels in patients with reflux esophagitis when given either 20 mg daily (group 1) or on alternate days (group 2). During the follow-up period, clinical remission was monitored and maintained in all patients in group 1 and in the majority of patients in group 2.

RESULTS

The mean serum gastrin level was significantly elevated in group 1 (mean +/- SE, 159 +/- 23.6 pg/mL; range, 45-620 pg/mL; n = 31) as compared with the alternate-day treatment group (group 2) (66 +/- 4.8 pg/mL; range, 37-115 pg/mL; n = 21) (p < 0.005). In controls, serum gastrin levels showed similar values to those found in group 2 (54 +/- 4.3 pg/mL; range, 27-94 pg/mL; n = 20). Fourteen patients (45%) in group 1 had serum gastric ranging from 140 to 620 pg/mL, and 8 (25%) had a 6-fold or greater increase in serum gastrin. The follow-up treatment period ranged between 3 and 60 months (mean +/- SE, 16.1 +/- 2.1 months) for group 1 and 3-36 months (9.7 +/- 1.4 months) for group 2. Upon multivariate adjustment for age and duration of treatment, a significantly lower mean serum gastrin level was observed in the alternate-day group as compared with the daily treated group.

CONCLUSION

Alternate-day, long-term treatment with omeprazole may be adequate to maintain remission in patients with reflux esophagitis. This regimen can assure serum gastrin levels within the normal range, thus reducing the potential risk of prolonged, sustained hypergastrinemia and profound hypochlorhydria.

Acid peptic disease in the elderly

GERD and peptic ulcer disease are important diseases in the elderly. GERD presents similarly in the elderly and the young, although elderly patients may have less severe symptoms yet more severe mucosal disease and a higher prevalence of BE. Although the prevalence of H. pylori is falling, the elderly remain at risk for peptic ulcer because of the widespread use of NSAIDS. The presentation of peptic ulcer disease in the elderly can be subtle and atypical when compared with younger patients, leading to a delay in diagnosis. Because of comorbidity in the aged, peptic ulcer disease and its complications result in increased morbidity and mortality rates.

Assay of omeprazole and omeprazole sulfone by semi-microcolumn liquid chromatography with mixed-function precolumn

A column-switching system based on semi-microcolumns was used for direct analysis of omeprazole and omeprazole sulfone in human plasma samples. Plasma samples were injected into a mixed-function (MF Ph-1) column (35 mmx4.6 mm I.D.) to remove proteins and other non-specific peak producing substances from the analyte-containing time zone. The analyte-containing fraction was thereafter transferred to a C-18 semi-microcolumn (250 mmx1.5 mm I.D.) after concentration at the C-18 intermediate column. The absorbance at 302 nm in a ultraviolet (UV) detector was recorded to measure the concentration. The detection limit for omeprazole and omeprazole sulfone in the present method was 10 ng/ml. Interbatch variation (coefficient of variation) of the QC samples spanned less than 10% and intra-batch variation less than 2%. The recovery ratios of omeprazole and omeprazole sulfone were over 98%. The current method can be used as a simpler procedure with similar sensitivity and reproducibility as previously reported methods.

Overuse of proton pump inhibitors

BACKGROUND

There have been concerns raised about the potential adverse effects of proton pump inhibitors, especially with long-term use. In particular, their potent action can suppress the features and delay the diagnosis of gastric cancer, while prolonged exposure may hasten the development of gastric carcinoids.

AIM

To examine the use of proton pump inhibitors in patients at the major teaching hospital in Tasmania, Australia, principally to determine the appropriateness of the therapy according to published guidelines.

METHODS

A retrospective review of the medical records of all patients prescribed any of the proton pump inhibitors at the hospital over a 7-month period, was performed. An extensive range of demographic and clinical variables was recorded for each patient. The patients were also asked a series of questions during their hospitalization to extract some of the relevant information - in particular, if and when they had undergone endoscopy.

RESULTS

The 200 patients (52% males) had a mean age of 69 +/- 16.4 years. The most common indications for using proton pump inhibitors were acute gastrointestinal bleeding (20.9%), severe refractory ulcerating oesophagitis (17.3%), mild/moderate oesophageal reflux (17.3%) and refractory peptic ulcer (11.7%). A large number of patients were using a proton pump inhibitor for 'other' indications (39.6%). The prescribing of proton pump inhibitors satisfied the approved indications, as outlined in the Australian Schedule of Pharmaceutical Benefits, in only 37.1% of cases. Endoscopy had been performed in 54.1% of patients prior to commencing therapy with a proton pump inhibitor and within the next 7 days in another 12.8% of patients. Only 59% of patients had previously been treated with an H2-receptor antagonist before commencing therapy with a proton pump inhibitor. Even worse, only 58.5% of patients had used an H2-receptor antagonist before a proton pump inhibitor for mild/moderate oesophagitis. The median duration of proton pump inhibitor therapy for patients admitted to the hospital and already receiving one of the drugs was 450 days. Over half of the patients were being concurrently treated with other drugs which are known to cause or exacerbate gastro-oesophageal disease, and 18% were smokers.

CONCLUSION

Whereas the proton pump inhibitors are undoubtedly effective agents, studies of their prescribing in practice consistently suggest over-use prior to endoscopy, use in patients who do not fit the approved criteria, and prescribing for indications in which 'less powerful' agents should have been sufficiently effective for the patient's symptoms. This poses economic and safety concerns, particularly in light of the suggestion that these drugs could delay the diagnosis of gastric cancer.

Pharmacologic strategies for treating gastroesophageal reflux disease

OBJECTIVE

This paper presents a synopsis of the pathophysiology of gastroesophageal reflux disease (GERD) and the efficacy, safety, and cost of the agents commonly used in its treatment.

BACKGROUND

Symptomatic relief of GERD can be obtained with lifestyle changes (avoidance of factors that may exacerbate symptoms, such as overeating and use of alcohol and tobacco) and use of over-the-counter medications such as antacids or histamine-2 (H2)-receptor antagonists. When these measures are unsuccessful, treatment with prescription-strength medications is required to prevent complications, such as Barrett's esophagus or esophageal adenocarcinoma.

METHODS

Current guidelines for the management of GERD were identified through a MEDLINE search of the English-language literature from January 1995 through December 1999 and a search of the bibliographies of identified articles.

CONCLUSION

Patients who do not respond to initial therapy should be managed with prescription-strength H2-receptor antagonists. Endoscopy should be considered for patients with atypical or refractory symptoms. Patients with a confirmed diagnosis of refractory GERD, severe esophagitis, Barrett's esophagus, or peptic stricture should be treated with and maintained on a proton-pump inhibitor.

Effect of proton pump inhibitor alone or in combination with clarithromycin on mycobacterial growth in human alveolar macrophages

The effect of omeprazole, a clinically used proton pump inhibitor, alone or in combination with clarithromycin was evaluated against Mycobacterium avium, Mycobacterium intracellulare and Mycobacterium tuberculosis, using a human alveolar macrophage model of infection. Omeprazole exhibited no significant effect on the growth of the two M. avium complex strains or on the mycobactericidal activity of clarithromycin against them. In contrast, omeprazole significantly promoted the growth of Mycobacterium tuberculosis and the anti-mycobacterial activity of clarithromycin against it in human alveolar macrophages. It was speculated that intracellular acidic milieu around M. tuberculosis might be one reason for the lower activity of clarithromycin in the treatment of human tuberculosis.

Gastrointestinal pharmacology

Diseases of the gastrointestinal tract that require pharmacologic management, usually in combination with other treatments, are gastric ulcers (omeprazole and others), colic (laxatives, analgesics), diarrhea (antibiotics, protectants and absorbents, glucocorticoids, motility inhibitors), reperfusion injury, postoperative ileus (prokinetic drugs), and adhesions. There is growing evidence that nonsteroidal anti-inflammatory drugs can alter important physiologic properties of the intestine; however, these drugs are valuable analgesics for horses and their use should be tempered with an awareness of their harmful effects. The role of antibiotics in treating gastrointestinal disease is controversial, but their ability to induce life-threatening diarrhea is well known and invites caution and defensible use of these drugs in horses.

Comparison of derivative spectrophotometric and liquid chromatographic methods for the determination of omeprazole in aqueous solutions during stability studies

A first derivative spectrophotometric method was developed for the determination of omeprazole in aqueous solutions during stability studies. The derivative procedure was based on the linear relationship between the omeprazole concentration and the first derivative amplitude at 313 nm. The first derivative spectra was developed between 200 and 400 nm (deltalambda = 8). This method was validated and compared with the official high-performance liquid chromatography (HPLC) method of the USP. It showed good linearity in the range of concentrations studied (10-30 microg ml(-1)), precision (repeatability and inter-day reproducibility), recovery and specificity in stability studies. It also seemed to be 2.59 times more sensitive than the HPLC method. These results allowed to consider this procedure as useful for the rapid analysis of omeprazole in stability studies since there was no interference with its decomposition products.

Review article: current perspectives on hypergastrinaemia and enterochromaffin-like-cell hyperplasia

Rabeprazole, a new benzimidazole proton pump inhibitor (PPI), is among a class of agents known to be very potent inhibitors of gastric acid secretion. PPIs inhibit hydrogen-potassium adenosine triphosphatase activity on the luminal surface of the parietal cell, effectively blocking the final common pathway for gastric acid secretion. Raising gastric pH stimulates the production of gastrin by G cells in the antrum of the stomach, which can lead to enterochromaffin-like (ECL)-cell hyperplasia. In the past, these changes have been viewed with concern, particularly in the light of studies in rats indicating that hypergastrinaemia and ECL-cell hyperplasia induce gastric carcinoid tumour formation. All available clinical data indicate that long-term PPI use does not lead to carcinoid tumour formation in humans. In fact, both serum gastrin elevation and ECL-cell hyperplasia are now generally viewed as normal physiological responses to gastric acid suppression. Serum gastrin concentrations, in particular, correlate well with gastric acid suppression, which has led to the use of gastrin response by some investigators as a surrogate marker of antisecretory effectiveness. Long-term tolerability data indicate that PPIs have a favourable side-effect profile. Data obtained from patients receiving acute or long-term maintenance rabeprazole therapy support this conclusion. Furthermore, neither animal nor human data obtained with rabeprazole suggest a significant risk for neoplastic changes secondary to hypergastrinaemia.

Nocturnal asthma: role of nocturnal gastroesophageal reflux

Gastroesophageal reflux (GER) is common in those with asthma, with 77% of asthmatics complaining of heartburn, with 41% experiencing reflux-associated respiratory symptoms. Likewise, 24% of those with asthma that is difficult to control have "clinically silent" GER. There are no studies examining nocturnal reflux symptoms in asthmatics. Esophageal dysmotility is also common, and abnormal esophageal acid contact times on 24h esophageal pH tests were found in 82% of asthmatics examined consecutively. Most asthmatics with GER also have abnormal esophageal acid contact times while in the supine position, reflecting sleep time. Endoscopic evidence of esophagitis was found in 43% of asthmatics. Two mechanisms of bronchoconstriction induced by esophageal acid have been proposed: a vagally mediated reflex, by which esophageal acid in the distal esophagus causes reflex bronchoconstriction, and microaspiration. Although there is conflicting evidence, distal esophageal acid causes a decrease in peak expiratory flow rates, an increase in respiratory resistance, and an increase in minute ventilation. If microaspiration is present, there is further augmentation of this airway response. Although only a few studies have been performed in those with nocturnal asthma with GER, one study in a pediatric population showed that esophageal acid infusions caused more airway responses at 04:00 than at 24:00. Also, asthmatic children with nocturnal asthma symptoms have a higher reflux score, with a positive correlation between reflux score and nighttime-associated wheezing. Despite these findings in children, a study performed in sleeping adults with nocturnal asthma noted no alterations in airflow resistance with esophageal acid, concluding that GER contributed little to the nocturnal worsening of asthma. There are also gastroesophageal circadian issues that may influence GER in asthmatics. Gastric acid secretion peaks at approximately 21:00, and gastric emptying is delayed when a meal is given at 20:00 versus 08:00. Esophageal acid clearance is delayed significantly during sleep, and acid clearance occurs during arousals. Upper esophageal sphincter (UES) pressure also decreases with sleep onset, which may predispose to microaspiration. Further research is needed to clarify what role nocturnal reflux has on nocturnal asthma and airway inflammation and whether circadian rhythm factors alter airway responses to esophageal acid.

Lansoprazole versus omeprazole for duodenal ulcer healing and prevention of relapse: a randomized, multicenter, double-masked trial

The aim of this randomized, multicenter, double-masked, parallel-group study was to compare the efficacy of lansoprazole with that of omeprazole monotherapy in duodenal ulcer healing and prevention of relapse. A total of 251 patients with duodenal ulcer were treated with either lansoprazole 30 mg/d (n = 167) or omeprazole 40 mg/d (n = 84). Patients with healed ulcers were then randomly allocated to 12 months of maintenance therapy with lansoprazole 15 mg/d (n = 74), lansoprazole 30 mg/d (n = 71), or omeprazole 20 mg/d (n = 73). Healing rates at 4 weeks (intent-to-treat analysis) were 93.9% (95% confidence interval [CI], 90.2% to 97.6%) with lansoprazole and 97.5% (95% CI, 93.7% to 100%) with omeprazole; there were no significant differences between groups. Endoscopic relapse rates after 6 months were 4.5% (95% CI, 0% to 10.6%) with lansoprazole 15 mg, 0% with lansoprazole 30 mg, and 6.3% (95% CI, 1.5% to 12.5%) with omeprazole 20 mg, compared with 3.3% (95% CI, 0% to 8.2%), 0%, and 3.5% (95% CI, 0% to 8.8%), respectively, at 12 months. Again, there were no significant differences between groups. The incidence of adverse events during acute treatment was 6.0% and 7.1% in the lansoprazole and omeprazole groups, respectively; during maintenance therapy, the incidences were 12.2% (lansoprazole 15 mg), 5.6% (lansoprazole 30 mg), and 11.0% (omeprazole 20 mg). Within treatment groups, pain was significantly ameliorated after the acute phase but not after maintenance therapy (P < 0.05); no differences were observed between groups. Gastrin values increased significantly after acute therapy (P < 0.05), persisted at these increased levels during maintenance therapy, and returned to normal after 6-month follow-up. Both lansoprazole and omeprazole were highly effective and well tolerated in the treatment of duodenal ulcer; relapse rates were similar for all doses studied. Thus no additional benefit is to be gained from using a proton-pump inhibitor at a dose > 15 mg lansoprazole to prevent relapse.

Review article: the pharmacology of rabeprazole

Rabeprazole sodium is a new substituted benzimidazole proton pump inhibitor with several differences compared with existing proton pump inhibitors. In vitro and animal studies have demonstrated that rabeprazole is a more potent inhibitor of H+,K(+)-ATPase and acid secretion than omeprazole, and is a more rapid inhibitor of proton pumps than omeprazole, lansoprazole, or pantoprazole. This probably reflects rabeprazole's faster activation in the parietal cell canaliculus. In human studies, once-daily doses of 5-40 mg of rabeprazole inhibit gastric acid secretion in a dose-dependent fashion. A once-daily dose of 20 mg has consistently achieved profound decreases in 24-h intragastric acidity in single and repeat dosing studies, in healthy volunteers and patients with either peptic ulcer disease or gastro-oesophageal reflux disease. Significantly greater decreases in intragastric acidity are achieved on day 1 of dosing with rabeprazole 20 mg than with omeprazole 20 mg. As with other proton pump inhibitors, rabeprazole has in vitro antibacterial activity against Helicobacter pylori, with greater activity against this organism than either lansoprazole or omeprazole. In addition to inhibiting bacterial urease activity, rabeprazole binds to several molecules on H. pylori. Clinical trials are needed to assess the clinical importance of these findings, as well as to assess whether the potential advantages of rabeprazole result in clinical benefit for patients with acid-related diseases.

[Proton pump inhibitors in pediatrics]

For the past ten years or so, proton pump inhibitors (PPI) such as omeprazole, lansoprazole, or pantoprazole, have become the reference treatment for peptic disorders in adults. PPIs have recently begun to be used in pediatrics, and this use is likely to expand. They act on the final step of gastric acid secretion by completely inhibiting the ATPase (proton pump) at the surface of the gastric parietal cells, thus yielding long term inhibition which is not correlated with the plasma concentration of the drug, in contrast to the effects of H2-blocker drugs. Our knowledge of this new class of treatment in pediatrics is still fragmentary, but the reported pharmacokinetic and clinical data indicate that they are suitable for use in children. While the short-term risk of complications appears to be minimal, the tolerance of these drugs in chronic use requires careful monitoring because of the potential consequences of prolonged inhibition of acid secretion.

Comparison of rabeprazole 20 mg versus omeprazole 20 mg in the treatment of active duodenal ulcer: a European multicentre study

BACKGROUND

Rabeprazole sodium is the newest member of a class of substituted benzimidazole molecules known as proton pump inhibitors. Other proton pump inhibitors have been shown to be effective in healing active duodenal ulcer.

METHOD

This randomized, double-blind, multicentre study, conducted at 25 European sites, compared the efficacy and tolerability of rabeprazole and omeprazole in patients with active duodenal ulcers. One hundred and two patients with active duodenal ulcer received rabeprazole 20 mg and 103 patients omeprazole 20 mg once daily for 2 or 4 weeks, with ulcer healing monitored by endoscopy.

RESULTS

After 2 weeks, complete ulcer healing was documented in 69% of patients given rabeprazole 20 mg and in 62% of patients given omeprazole 20 mg (N.S.). After 4 weeks, healing rates were 98% in the rabeprazole group and 93% in the omeprazole group (P = 0.083). Rabeprazole-treated patients had significantly greater improvement in daytime pain symptom relief than those treated with omeprazole at the conclusion of the study (P = 0.038). Both drugs were well tolerated over the 4-week treatment period. Mean changes from baseline to end-point in fasting serum gastrin were significantly greater in the rabeprazole group, but at end-point mean values were well within normal limits for both groups. No clinically meaningful changes or other between-group differences were observed in laboratory parameters.

CONCLUSION

In this study, rabeprazole produced healing rates equivalent to omeprazole at weeks 2 and 4, and provided significantly greater improvement in daytime pain. Both treatments were well tolerated.

Upper gastrointestinal tract bleeding in critically ill pediatric patients

Similar to adults, children under physiologic stress can develop an imbalance in defensive (mucosal layer, motility) and aggressive (gastric acid, bile salts, enzymes) factors responsible for maintaining a healthy gastrointestinal tract. Hypoxia in the gastrointestinal tract likely disrupts the defensive factors, thereby permitting damage by aggressive factors to upper gastrointestinal epithelium that may progress to stress ulceration and acute upper gastrointestinal tract bleeding (UGIB). The basic pathophysiology may be similar in children and adults; however, differences in the time to developing ulceration, ulcer location, and number of ulcers have been reported. Functional development of the gastrointestinal tract is influenced by disease, gestational and postnatal age, and exposure to and type of enteral feedings, thereby confounding the development and prophylaxis of UGIB in neonates and infants. In addition, pharmacotherapy decisions are often complicated by drug administration issues and adverse effects.

Review article: Helicobacter pylori and gastro-oesophageal reflux disease-clinical implications and management

A significant proportion of patients with gastro-oesophageal reflux disease (GERD) have Helicobacter pylori infection, but it is unclear whether or not H. pylori should be treated in this clinical setting. The aim of this review was to critically assess the relationship between H. pylori and GERD and its potential implications for the management of GERD. Data for this review were gathered from the following sources up to April 1998-the biomedical database MEDLINE, a detailed review of medical journals, and a review of abstracts submitted to relevant international meetings. On average, 40% of GERD patients carry H. pylori infection, with a reported infection prevalence ranging from 16% to 88%. To date, there has been no reported controlled trial of effective H. pylori therapy in GERD. GERD has been reported to develop de novo following the cure of H. pylori in peptic ulcer disease. In the presence of H. pylori, proton pump inhibitor therapy appears to accelerate the development of atrophic corpus gastritis, a potentially precancerous condition. Conversely, proton pump inhibitor therapy seems to become less effective after cure of H. pylori. The mechanisms underlying these important contrasting phenomena are poorly understood. The relationship between H. pylori and GERD is complex, and it is difficult to give definitive guidelines on the management of H. pylori infection in GERD. Controlled trials of H. pylori therapy in GERD are urgently needed, as well as further long-term data on both the natural history of gastric histopathological changes in the H. pylori-positive GERD patient treated with proton pump inhibitors, and the impact of H. pylori status on the clinical efficacy of antisecretory therapy. Pending these data, it is perhaps advisable to advocate cure of H. pylori in young patients with proton pump inhibitor-dependent GERD who, in the absence of anti-reflux surgery, are faced with the likelihood of long-term medical therapy.

Gastroesophageal reflux disorders and asthma

Gastroesophageal reflux (GERD) may trigger asthma. Approximately 77% of asthmatic people experience reflux symptoms, although GERD may be clinically silent in some. Esophagitis is found in 43% of asthmatic people, and 82% have abnormal esophageal acid contact times on esophageal pH testing. Clearly, GERD is prevalent in asthmatic people. Pathophysiologic mechanisms of acid-induced bronchoconstriction include a vagally mediated reflex and microaspiration. Whether these airway responses are clinically significant is the subject of some debate. Interestingly, peak expiratory flow rates and specific airway resistance alterations persist despite esophageal acid clearance. Preliminary evidence shows that substance P, an inflammatory mediator that causes airway edema, is released with esophageal acid. Although therapeutic studies are limited by their small population sizes and study design, up to 70% of asthmatic people have asthma improvement with antireflux therapy. Possible predictors of asthma response include patients with symptomatic esophageal regurgitation; abnormal proximal esophageal acid exposure; and, in surgical studies, those with normal esophageal motility and asthma response with medical therapy. Future research will further define the association between asthma and gastroesophageal reflux.

The utility of endoscopy in the management of patients with gastroesophageal reflux symptoms

OBJECTIVE

The utility of endoscopy in the management of patients with symptoms of gastroesophageal reflux disease (GERD) is unclear. The purpose of this prospective study was to assess the impact of endoscopy on the subsequent management of patients with uncomplicated reflux symptoms.

METHODS

A total of 742 patients underwent endoscopy for symptoms of GERD. Endoscopists recorded the therapy before endoscopy, the findings of endoscopy, and the treatment recommendations after endoscopy.

RESULTS

There was no difference in pre-endoscopy therapy or grade of esophagitis in subjects undergoing endoscopy for failed therapy versus GERD symptoms alone. After endoscopy, the most common strategy for patients taking omeprazole was to maintain or increase the dose. For those taking an H2 blocker before endoscopy, the most common outcome was to switch the patient to omeprazole, independent of the grade of esophagitis.

CONCLUSIONS

Most patients undergoing endoscopy for symptoms of GERD were switched to omeprazole regardless of the endoscopic findings. No esophageal cancer was identified and the incidence of Barrett's esophagus was low. It appears that endoscopy itself did not change the management of patients receiving H2-blocker therapy. A trial of a proton pump inhibitor before endoscopy should be considered.

Antiulcer drug prescribing in hospital successfully influenced by "immediate concurrent feedback"

OBJECTIVE

To determine whether immediate concurrent feedback (ICF) focused on inpatient omeprazole prescribing achieved more rational and cost-effective antiulcer drug prescribing and usage.

METHODS

In a 1400-bed teaching hospital, an audit (by specially trained personnel) was conducted to monitor inpatient prescribing of omeprazole (1) in preference to H2-antagonists and other drugs according to agreed criteria (Helicobacter pylori eradication, severe reflux esophagitis, rapid ulcer healing deemed urgent because of severe symptoms or complications, high-dose steroid therapy of > or =30 mg/day prednisolone) and (2) appropriateness of intravenous dosing (oral route not feasible or contraindicated). After baseline monitoring for 1 month, followed by relevant antiulcer drug therapy education, ICF was instituted for 1 year. This entailed explanatory memoranda requesting a change in prescribing issued to the respective medical teams of patients whose omeprazole prescription did not "conform." The main outcomes of the study were omeprazole prescription numbers per month and the proportion conforming, defined daily doses of antiulcer drugs used and corresponding expenditures, and pertinent antiulcer drug utilization data from 9 other local hospitals.

RESULTS

Baseline omeprazole prescribing conformed in 32 of 173 (18%) of the patients compared with 451 of 546 (83%) during institution of ICF (P < 0001; chi2 test). Correspondingly, average overall omeprazole and ranitidine usage (inpatient and outpatient) and expenditure decreased (44% and 45%, respectively); collectively, use of less expensive alternatives increased about 61%. Estimated savings averaged about HK$150,000 ($20,000) per month. No comparable changes in usage were noted in 9 other local hospitals.

CONCLUSION

Regarding hospital antiulcer drugs, this ICF strategy was associated with more rational prescribing and usage, and an important saving of resources.

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.

Does medical antireflux therapy improve asthma in asthmatics with gastroesophageal reflux?: a critical review of the literature

OBJECTIVE

Identify and critically review the peer-reviewed, English-language studies of the effects of medical antireflux therapy in asthmatics with gastroesophageal reflux (GER).

DESIGN

Using the 1966 to 1996 MEDLINE database, asthma was combined with GER to identify all studies of the effects of medical antireflux therapy on asthma control. The articles' bibliographies were also reviewed. Studies were graded according to Sackett's criteria and grouped by levels of evidence.

RESULTS

A total of 242 citations were found; 171 were published in English. Twelve studies of the effects of medical antireflux therapy on asthma control, with a total of 326 treated patients, were identified. Eight studies were placebo-controlled, three were open studies, and one used an untreated control. Eight studies treated 20 or fewer patients. Reflux symptoms either did not improve or the effects of antireflux therapy on them were not reported in four studies. The combined data from the controlled medical antireflux studies showed that: (1) asthma symptoms improved in 69% of the subjects; (2) asthma medication use was reduced in 62% of the subjects; (3) evening peak expiratory flow (PEF), but not PEF at other times, improved in 26% of the subjects; and (4) spirometry did not improve in any of the placebo-controlled antireflux studies.

CONCLUSIONS

Analysis of the combined data suggests that medical antireflux therapy improves asthma symptoms, may reduce asthma medication use, but has minimal or no effect on lung function.

Nocturnal recovery of gastric acid secretion with twice-daily dosing of proton pump inhibitors

OBJECTIVES

It is our experience that many patients treated with proton pump inhibitors (PPI) b.i.d. recover acid secretion during the night. Our aim was to assess the efficacy of omeprazole and lansoprazole b.i.d. on nocturnal gastric acidity.

METHODS

Three groups were studied with intragastric pH monitoring. Group 1 consisted of 17 patients with gastroesophageal reflux disease (GERD) taking omeprazole 20 mg b.i.d. Group 2 was 16 male volunteers taking omeprazole 20 mg b.i.d. and Group 3 comprised 12 volunteers taking lansoprazole 30 mg b.i.d.

RESULTS

The percentages of time that subjects had pH < 4 were lower during supine than upright periods in Groups 1 and 3 (P < 0.01). Recovery of nocturnal acid secretion lasting > 1 h, termed acid breakthrough, occurred in three-fourths of all individuals within 12 h from intake of the evening dose of PPI. Median time to acid breakthrough for the whole group was 7.5 h.

CONCLUSION

Nocturnal acid breakthrough occurs in a majority of patients and normal volunteers taking PPI b.i.d.

Lack of pharmacokinetic interaction between mexiletine and omeprazole

OBJECTIVE

To investigate the effect of omeprazole on the pharmacokinetics of mexiletine.

METHODS

Nine healthy male Japanese volunteers participated in a crossover study. On day 1, the subjects received mexiletine 200 mg. On days 2-7, they received omeprazole 40 mg, and on day 8 they received mexiletine 200 mg and omeprazole 40 mg concomitantly. Serum concentrations of mexiletine were determined just before drug administration and at 1, 2, 3, 4, 6, 8, 12, and 24 hours on day 1 and day 8.

RESULTS

No differences in mexiletine concentrations were observed between the two phases of the study. The mean AUCs after administration of mexiletine alone and in combination with omeprazole 40 mg/d were 6.26 and 6.20 ng.h/L, respectively.

CONCLUSIONS

These findings suggest that omeprazole does not affect mexiletine metabolism.

Gastrointestinal diseases in women

Gastrointestinal disorders are among the most common disorders for which women seek medical attention. Most gastrointestinal diseases in women are not inherently different from those that occur in men. There are several disorders, however, that occur more frequently or manifest themselves differently in women. This article reviews common gastrointestinal disorders affecting women. The pathophysiology, clinical manifestations, management, and gender-specific issues of gastroesophageal reflux disease, peptic ulcer disease, irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD) are discussed.

A scoring system for gastric ulcers in the horse

Five investigators familiar with gastric ulcer disease in horses met to establish a scoring system that could be utilised in future studies. Slides of gastric lesions were viewed and discussed and a scoring system established that required the nonglandular and glandular portions of the stomach to be graded separately. Each portion of the stomach (glandular and nonglandular) received a score for number of ulcers present and a score for severity of ulcers which resulted in each stomach receiving 4 separate scores. After the grading system was developed, each investigator independently graded 16 horses with gastric ulcer disease that had been previously recorded on video tape. The results of each investigator's scores were then compared. There was a variability between observers in the scores for severity of both nonglandular and glandular lesions but the variability was not significant. The variability between observers for the number of glandular lesions was also not significant. This implied that there was consistency between the 5 observers in the way severity of lesions was scored and the number of glandular lesions. However, there was a significant variability between observers for the number of nonglandular lesions which implied agreement on this observation was more variable.

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.

Omeprazole, a specific gastric secretion inhibitor on oxynticopeptic cells, reduces gizzard erosion in broiler chicks fed with toxic fish meals

The relation between gizzard erosion-black vomit (GE-BV) and gastric secretion is not completely understood. A pharmacological approach to reduce the presence of GE-BV in chicks due to fish meal in diets is also unknown. In this study the use of omeprazole, a H+/K+ ATPase inhibitor, and fish meals of different biotoxicological characteristics, showed that: 1) Omeprazole decreased total gastric acid content, GE scores and severe GE (SGE) cases, in a dose-dependent manner. This reduction was significant at levels higher than 20 mg omeprazole/Kg body weight (BW)/day (p < 0.01). The addition of 50 mg omeprazole/kg BW/day almost completely prevented the incidence of SGE cases and reduced in 50% GE score in chicks (p < 0.01). 2) A significant reduction in specific mortality, near 90%, was also seen with all toxic fish meals when omeprazole (50 mg/Kg BW/day) was added to experimental diets in comparison to control groups. However, no mortality was observed when omeprazole was added to diets containing non-toxic fish meals. 3) In chicks fed with toxic fish meals, addition of different amounts of omeprazole to diets changed the relative weight of proventriculus (p < 0.01) and gizzard (p < 0.05). Maximum effect was obtained with omeprazole concentration higher than 50 mg/Kg BW/day. 4) Omeprazole did not change feed intake in chicks fed with toxic fish meal. However, in some fish meal a reduction on weight gain was observed with the addition of omeprazole.

Determinants of initiation and suboptimal use of anti-ulcer medication: a study of the Quebec older population

OBJECTIVES

To describe the use of anti-ulcer medication in the Quebec older population; to examine determinants of initiation, suboptimal use, and switches between products.

DESIGN

Population-based retrospective cohort study.

SETTING

Universal health program for older adults in Quebec.

PARTICIPANTS

5000 users and 5000 non-users of anti-ulcer medications were selected randomly. Use was defined as the presence in the 1991 prescription database of an anti-ulcer prescription. Among users, 1697 (34%) were new users and were considered as the exposure group. Subjects were followed for 365 days after inclusion.

MEASUREMENTS

Measured were patient's age, gender, prescribed duration of anti-ulcer medication, concomitant medications, and gastrointestinal diagnostic procedures.

RESULTS

A total of 17% of new users had unusually short courses; 18% were long-term users. There was no difference in duration for omeprazole compared with other anti-ulcer medications. First-time use of NSAIDs was the strongest predictor of initiation of anti-ulcer medication (odds ratio = 3.21; 95% CI, 2.66-3.88). Twenty-six percent of users switched brands. Only 9.5% of new users underwent a diagnostic procedure before initiation of therapy, and 49% of long-term users ever underwent such procedure.

CONCLUSION

Despite a relatively homogeneous recommended duration of therapy, patterns of use of anti-ulcer medication among older people are highly variable, and treatment is often not accompanied by a diagnostic procedure.

The effects of oral doses of lansoprazole and omeprazole on gastric pH

We compared gastric pH values after therapeutic doses of lansoprazole and omeprazole in 17 healthy adult men. The pharmacokinetics of the two drugs were studied. A three-way crossover design compared the effects on gastric pH of 15 and 30 mg lansoprazole and 20 mg omeprazole--each given once daily for 5 days. Ambulatory 24-h intragastric pH levels were measured before dosing, after the first and fifth doses in each period, and 15 days after each dosing period. A positive relationship between the lansoprazole or omeprazole area under the curve (AUCs) and the 24-h mean pH values was found for each regimen. No differences in maximum concentration (Cmax) and AUC were noted from day 1 to day 5 for the two lansoprazole doses. With omeprazole, both Cmax and AUC levels were greater on day 5 than on day 1. All three regimens increased 24-h mean gastric pH, although 30 mg lansoprazole had the most significant effect. The percentage of time that gastric pH was >3, >4, and >5 was also significantly higher with 30 mg lansoprazole. All three regimens were associated with reversible elevations of serum gastrin, which more than doubled at some points. No clinically significant adverse events were documented.

Prevention of recurrences of erosive reflux esophagitis: a cost-effectiveness analysis of maintenance proton pump inhibition

PURPOSE

To determine the cost-effectiveness of three management strategies for healed erosive reflux esophagitis: maintenance therapy with a proton pump inhibitor (PPI) from the outset; no maintenance therapy unless a patient's symptoms recur once over a year; and no maintenance therapy unless a patient's symptoms recur twice over a year.

MATERIALS AND METHODS

Decision analysis using data from randomized trials of lansoprazole, case series, and expert opinion.

RESULTS

For patients with grade 4 esophagitis, maintenance from the outset is the most efficient approach. For all other patients, providing maintenance PPI after a patient experiences two recurrences is the least costly but least effective approach. The other two approaches prevent more recurrences: waiting to initiate maintenance therapy until symptoms recur once requires an additional $73 for each recurrence prevented whereas maintenance PPI from the outset requires an additional $819 for each recurrence prevented. Maintenance therapy from the outset is cost effective if symptoms of esophagitis cause a 22% or greater decrement in quality of life (using $50,000 per quality-adjusted life year gained as a cost-effectiveness definition). However, withholding maintenance until the time of a first recurrence is cost effective if symptoms cause a 2% or greater decrement in quality of life.

CONCLUSION

For grades 2 and 3 esophagitis, providing maintenance therapy after a patient experiences a further recurrence is a preferred option that appears cost-effective across a wide array of assumptions. Maintenance therapy from the outset, however, appears cost-effective only for those patients who report a significant decline in quality of life associated with esophagitis or for those patients with baseline grade 4 esophagitis.

Misoprostol and omeprazole in the prevention of chemotherapy-induced acute gastroduodenal mucosal injury. A randomized, placebo-controlled pilot study

BACKGROUND

Chemotherapy (CT) may induce acute mucosal injury to the stomach and duodenum, but its prevention has been scarcely investigated.

METHODS

One hundred and eighty-two cancer patients with normal stomach and duodenum or having fewer than 3 erosions, selected to be treated with cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) (77 breast carcinoma patients) or 5-fluorouracil (5-FU) (105 colon carcinoma patients), were randomly assigned to prophylactic treatment with misoprostol, 400 micrograms twice a day; omeprazole, 20 mg once a day; or placebo, 1 tablet twice a day. Seven days after the end of the second source of CT, all patients underwent control esophagogastroduodenoscopy. Endoscopic findings were quantified on the basis of an arbitrary score: 0 = normal; 1 = less than 3 erosions; 2 = 3-15 erosions; 3 = more than 15 erosions or ulcer; 4 = giant ulcer (greatest dimension of more than 2 cm) or multiple ulcers with cumulative greatest dimension exceeding 2 cm.

RESULTS

Mean score increased significantly in the placebo and misoprostol groups, either after CMF (P < 0.001 and P < 0.05, respectively) or after 5-FU (P < 0.001 for both), whereas it did not in the omeprazole group. Gastric and duodenal ulcers were significantly less frequent in patients receiving omeprazole than in those receiving placebo (P < 0.05 after both CMF and 5-FU). No significant difference was observed between placebo and misoprostol. Omeprazole was significantly more effective than placebo and misoprostol in reducing the frequency and degree of the endoscopic worsening, either after CMF or after 5-FU (P < 0.05 for both CT regimens). Epigastric pain and/or heartburn were significantly less frequent in patients receiving omeprazole than in those receiving placebo (P < 0.01) or misoprostol (P < 0.001).

CONCLUSIONS

The strong and prolonged inhibition of gastric acid production induced by omeprazole seems to be effective in preventing chemotherapy-induced gastroduodenal mucosal injury. Further trials are necessary to verify whether such a prevention of endoscopically observed injury can translate into prevention of clinically significant injury.

Differences between white subjects and Chinese subjects in the in vivo inhibition of cytochrome P450s 2C19, 2D6, and 3A by omeprazole

OBJECTIVES

To determine the effects of omeprazole on indexes of CYP2D6, CYP2C19 and 3A in vivo activity and to compare these in white subjects and Chinese subjects.

METHODS

Omeprazole, 40 mg/day, or placebo were administered in a double-blind crossover study for 3 weeks to eight healthy white and seven Chinese male extensive metabolizers of mephenytoin and debrisoquin. Debrisoquin (10 mg), dapsone (100 mg), and mephenytoin (100 mg) were given 1 week before administration, on the last day of administration, and 3 weeks after administration, and urine was collected over 8 hours. Phenotypic trait values were obtained from the urinary recoveries of the probe drugs or their metabolites.

RESULTS

In the white subjects, omeprazole significantly inhibited CYP2C19-mediated S-mephenytoin metabolism as indicated by decreases in the urinary R/S enantiomeric ratio (63% +/- 13%; p < 0.02; mean +/- SD) and the excretion of 4'-hydroxymephenytoin (39% +/- 13%; p < 0.001). Similar but smaller changes were also noted in Chinese subjects, 22% +/- 25% (p = 0.08) and 29% +/- 13% (p < 0.002), respectively. The interracial differences in the extent of inhibition of metabolism were statistically significant (p < 0.01 and p < 0.05, respectively). In contrast, the debrisoquin urinary metabolic ratio, a measure of CYP2D6, was unaffected. The excretion of hydroxylamine dapsone-a putative probe of CYP3A activity-was reduced by 40% +/- 30% (p < 0.03) in white subjects but not in Chinese subjects.

CONCLUSIONS

Omeprazole selectively inhibits the in vivo metabolism of S-mephenytoin, consistent with the predictions based on in vitro studies. The extent of interaction is greater in subjects of white European ancestry. It is to be expected that similar situations would also occur when omeprazole is coadministered with other substrates of CYP2C19.

Laparoscopic fundoplication

Most reports on laparoscopic fundoplication are from large, tertiary referral medical centers. Presented here is an experience by a single surgeon (M.E.F.) in community hospitals with 74 cases. All patients had esophagitis. All but two patients were Visick grade IV off medication. All patients had an incompetent lower esophageal sphicter. Four with abnormally low esophageal contractions underwent a Toupet procedure; the rest had a Nissen fundoplication. The largest estimated blood loss was 300 cc. One case (1.4%) had to be converted intraoperatively to an open procedure because of bleeding from an iatrogenic liver laceration. There were two minor complications (a urinary tract infection and a pneumothorax) and one death (massive liver necrosis with an otherwise unremarkable post mortem, thus it was felt to be due to anesthesia). The mean length of hospital stay was 2.8 +/- 0.21 days. Eighty-nine percent of the operations totally relieved reflux. Nineteen patients (26%) had mild, early postoperative dysphagia, gas bloat, and/or early satiety. Four patients did not get any improvement in their reflux, three still require chronic medication, and one underwent a redo open fundoplication. Three early patients had severe, new-onset postoperative dysphagia secondary to too tight a fundoplication. Attention must be focused on creating a loose wrap, a "floppy" Nissen by routine division of the short gastric vessels and the use of a large dilator in the esophagus when the fundoplication is constructed. Laparoscopic fundoplication is technically feasible, safe, and effective in a community hospital and does not require a large, tertiary referral medical center.

Ethnic and genetic determinants of omeprazole disposition and effect

OBJECTIVES

To compare the pharmacokinetics and dynamics of omeprazole in white and Chinese subjects.

METHODS

This double-blind two-stage study, performed in the clinical research center of a university hospital, evaluated 15 healthy nonsmoking men (eight white subjects and seven Chinese extensive metabolizers of mephenytoin). Blood samples were obtained over 24 hours after the eighth omeprazole dose (40 mg/day). Omeprazole, omeprazole sulfone, and hydroxyomeprazole pharmacokinetics were calculated from the respective plasma concentration-time curves. Twelve- and 24-hour integrated plasma gastriun (AUCgas12 and AUCgas24) were calculated from the respective plasma gastrin concentrations. A week before the initiation of omeprazole the activities of CYP2D6, CYP2C19, and CYP3A4 were determined by previously established methods.

RESULTS

Omeprazole concentrations were significantly lower (mean area under the plasma concentration time curve extrapolated to infinity [AUCO-infinity] +/- SEM; 7.53 +/- 1.21 versus 12.80 +/- 2.13 mumol.hr.L-1, respectively; p < 0.05) and its oral clearance greater (319 +/- 60 versus 183 +/- 35 ml/min, respectively; p < 0.05) in the white subjects than in the Chinese subjects. Omeprazole and omeprazole sulfone AUCO-infinity values were well correlated with the S/R mephenytoin ratio (r = 0.82 and r = 0.84, respectively; p < 0.001) and with urinary 4'-hydroxymephenytoin (r = -0.58 [p < 0.03] and r = -0.52 [p < 0.02], respectively). Fasting gastrin, AUCgas12, and AUCgas24 were significantly greater in the Chinese subjects than in the white subjects (30.0 +/- 6.4 versus 14.4 +/- 1.2 pmol, respectively [p < 0.02]; 661 +/- 114 versus 334 +/- 38 pmol.hr.L-1, respectively [p < 0.002]; and 1414 +/- 228 versus 747 +/- 99 pmol.hr.L-1, respectively [p < 0.004]). In addition, the S/R mephenytoin ratio and omeprazole AUCO-infinity correlated with the extent of omeprazole induced hypergastrinemia.

CONCLUSION

The metabolism of omeprazole and the rise in gastrin concentration after its administration is genetically determined and ethnically dependent.

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.