Functional analysis of the catalytic subunit of Dictyostelium PKA in vivo.

The catalytic subunit of the cAMP-dependent protein kinase (PKA) from Dictyostelium discoideum contains several domains, including an unusually long N-terminal extension preceding a highly conserved catalytic core. We transformed the aggregationless PkaC-null strain with several deletion constructs of both domains. Strains transformed with genes expressing catalytically-inactive polypeptides could not rescue development. Cotransformation with constructs encoding the N-terminal extension and the catalytic core, both unable to rescue development by themselves, yielded transformants able to proceed to late development. A 27-amino acid long hydrophobic region, immediately upstream of the catalytic core, was found indispensable for PKA function. A putative role of this sequence in the acquisition of the active conformation of the protein is discussed.

Prophage lambda libraries for isolating cDNA clones by functional screening.

Isolation of cDNA clones from lambda gt11 phage libraries by functional screening is limited by the low amount of lacZ-cDNA-encoded fusion protein synthesized in an isolated phage plaque. The amount of specific cDNA-encoded protein can be significantly enhanced by expression in bacterial colonies rather than phage plaques. Escherichia coli was lysogenized with a lambda gt11 cDNA expression library from Dictyostelium discoideum. Bacteria were selected for the presence of the lambda gt11 prophage by elimination of nonlysogenic parental cells with a lambda cI phage. The usefulness of the lysogen library was demonstrated by immuno-screening and functional screening with two different radiolabeled ligands. cDNA clones encoding a well-characterized D. discoideum protein, the regulatory subunit of the cAMP-dependent protein kinase, were isolated by screening the lysogen library with antibodies. Clones encoding this protein could also be identified by functional screening with [3H]cAMP, demonstrating that the limit of detection of positive clones by ligand screening is at least an order of magnitude lower for the lysogen library than for the corresponding phage library. We have subsequently used the lysogen library to isolate cDNA clones encoding calmodulin-binding protein(s) from D. discoideum by functional screening with [125I]calmodulin. For these clones, screening of the corresponding phage library had previously been found unsuccessful.

Comparative clinical trial of enprostil and ranitidine in the treatment of gastric ulcer.

In a randomized, double-bind, parallel, multi-clinic study, the safety and efficacy of enprostil (35 micrograms twice daily) and ranitidine (150 mg twice daily) were compared in the treatment of active gastric ulcer in 93 outpatients (47 enprostil-treated patients and 46 ranitidine). The two treatment groups were well matched for demographic characteristics. The healing rates in the enprostil group were 22, 58, 80, and 86 percent at two, four, six, and eight weeks, respectively. The corresponding rates in the ranitidine group were 22, 66, 84, and 89 percent. None of these differences was statistically significant. The area of the ulcer at baseline and smoking status did not appear to influence healing rates. There were no significant differences between treatment groups in time to relief of ulcer symptoms, frequency of daytime or nighttime ulcer pain, or antacid use. Side effects attributable to enprostil treatment were diarrhea (10 percent versus 6 percent with ranitidine), gastrointestinal pain, and vomiting. These side effects, however, did not influence the patients' assessments of their overall response to enprostil and ranitidine therapy. Six enprostil-treated patients and one ranitidine-treated patient withdrew from the trial prematurely because of adverse experiences. Monitoring of clinical laboratory test results showed no significant changes in the two treatment groups. This study demonstrates that a prostaglandin E2 analogue, enprostil, in a dose of 35 micrograms twice daily, is similarly safe and effective as ranitidine in the treatment of active gastric ulcer.

Optimal reduction of gastric acid secretion in the treatment of peptic ulceration.

Pronounced and sustained inhibition of acid secretion is currently the therapeutic principle most frequently applied in the treatment of peptic ulcer disease. Since theoretically short term risks of complete inhibition of acid secretion cannot be totally ruled out, anti-secretory anti-ulcer drugs should interfere as little as possible in the physiology of gastric acid secretion. This concept is presently best achieved through the single bedtime dose of H2-blockers, which has been shown to be as effective as a twice daily dosage regimen in peptic ulcer disease. This reduces only nocturnal acid secretion, while daytime acidity remains unaffected. But there is a close correlation between the extent of the reduction of nocturnal acid secretion, healing rates and pain relief. Additionally, large clinical trials with peptic ulcer patients have shown that after 14 days' treatment with H2-blockers 30 to 50% of patients still complain about ulcer pain and about 20 to 40% of patients take supplementary antacids. As a result of this there is undoubtedly a need for an additional medication that produces a more pronounced reduction of acidity than current treatment with H2-receptor antagonists as a single evening dose. Obviously this dosage regimen does not always fulfil the therapeutic requirements (i.e. pain relief) of the individual patient. Therefore a more flexible form of application should be introduced. In general clinical use it is not feasible to identify patients with a higher treatment requirement by acid secretion analysis. However, what is feasible is the recommendation to increase the dose and frequency of administration of H2-blockers in relation to the symptoms of pain.

Ca2+/calmodulin-binding proteins in Dictyostelium discoideum.

We have initiated a systematic study of Ca2+/calmodulin-regulated enzymes in the cellular slime mold Dictyostelium discoideum. Using 125I-labelled D. discoideum calmodulin (CaM) as a functional probe, several Ca2+/CaM-binding proteins were detected in crude cell lysates. Proteins with apparent molecular weights of 22 kDa and 78-80 kDa, respectively, were found in the soluble fraction. In addition, membrane-bound high molecular weight CaM-binding proteins were identified. Binding of CaM to all of the proteins required the presence of Ca2+ ions and competed efficiently with nonradioactive CaM from both Dictyostelium and bovine brain. The CaM antagonists melittin, W-7 and R24571 inhibited CaM binding. With a functional cloning approach, we previously obtained cDNA clones by screening a lambda gt11 lysogen expression library; in this paper, we report the analysis of CaM-binding activity by one of the recombinant cDNA clones in Escherichia coli. When rabbit antiserum was raised against it, the antiserum recognized a 78-80-kDa protein in Dictyostelium extracts which comigrated on SDS-polyacrylamide gels with 78-80-kDa CaM-binding activity.

Overexpression, purification and characterization of Dictyostelium calcineurin A.

The catalytic subunit of Ca2+/calmodulin-dependent protein phosphatase (calcineurin A) was overexpressed about 50-fold in Dictyostelium discoideum cells transformed with a vector containing the cDNA for D. discoideum calcineurin A under control of the actin-6 promoter. In crude lysates from the overexpressing cell line, high Ca2+/calmodulin-stimulated phosphatase activity was detected. Calcineurin A was purified by anion exchange chromatography and calmodulin-Sepharose affinity chromatography, and the enzymatic activity of the isolated protein was characterized. Its phosphatase activity was strictly dependent on the addition of divalent metal ions such as Mg2+ or Mn2+. Disulphide-reducing agents increased the activity more than 10-fold. Ca2+/calmodulin stimulated the activity by a factor of 2.5-5. Despite the high extra Ca2+/calmodulin-dependent phosphatase activity, the overexpressing cell line showed no phenotypic aberrations.

Efficacy of continuous therapy for peptic ulcer in controlled clinical trials.

Long-term studies have confirmed unequivocally the clinical efficacy of continuous therapy with H2-receptor antagonists in reducing the incidence of ulcer recurrence. However, studies have also reported varying relapse rates as a result of differences in study design, particularly the frequency of endoscopy and hence the detection of asymptomatic ulcer relapse. Risk factors for ulcer relapse include smoking, stress, previous history of frequent ulcer relapses, duration of disease for more than 10 years and concomitant administration of non-steroidal anti-inflammatory drugs. In the prevention of relapse with H2-receptor antagonists, choice of agents also may influence the rate of relapse. A meta-analysis of data from direct comparative trials indicates that recurrence rates of duodenal ulcer are significantly lower after one year of treatment with ranitidine (150 mg nocte) than with cimetidine (400 mg nocte). It has been claimed that patients with peptic ulcer disease can be successfully managed by intermittent courses of treatment with H2-receptor antagonists which are taken in response to the development of symptoms. However, high relapse rates (64-100%) have been reported during the first year of follow-up of patients who were receiving intermittent treatment with H2-receptor antagonists. High complication rates (haemorrhage 11.4%, perforation 1.2%) have also been reported over a seven-year follow-up, while continuous treatment with H2-receptor antagonists significantly decreases the risk of haemorrhage in the event of ulcer recurrence.

Enteric coating of aspirin significantly decreases gastroduodenal mucosal lesions.

BACKGROUND: Low-dose aspirin (acetylsalicylic acid, ASA) increases the risk of developing peptic ulceration. AIM: To investigate the gastroduodenal mucosal tolerability of enteric-coated ASA (EC-ASA) 100 mg/day compared to either placebo (study 1) or plain ASA 100 mg/day (study 2) in healthy volunteers. METHODS: Study 1: In this double-blind study 18 volunteers received randomized dosing with either EC-ASA 100 mg or placebo for 15 days. Study 2: 41 volunteers underwent randomized 7-day dosing of either EC-ASA 100 mg or plain ASA 100 mg in this double-blind, parallel-group, comparison study. In both studies acute gastroduodenal mucosal lesions were assessed endoscopically before treatment, on the morning of day 1 after the first dose (only in study 2), and on the morning after the last dose of the test medication. RESULTS: Study 1 did not reveal any significant differences between the lesion scores of EC-ASA and placebo. In contrast, in study 2 significantly higher total gastroduodenal mucosal lesion scores were observed on day 1 after the first dose and after 7 days of dosing with plain ASA (mean sum of the lesion scores in the gastric fundus, body, antrum and in the duodenal bulb: day 1: plain ASA 3.95+/-3.38 vs. EC-ASA 1.43+/-1.91, P = 0.03; day 7: plain ASA 6.35+/-4.10 vs. EC-ASA 2.00+/-2.02, P = 0.0004). Tolerance of the test drugs was good, and no other adverse events were observed. CONCLUSIONS: Enteric-coated aspirin 100 mg/day causes significantly less gastroduodenal damage over 7 days than the same dose of plain aspirin, when given to healthy subjects. There was little gastric injury and no significant differences between EC-ASA and placebo in this respect.

The effects of oral rabeprazole on endocrine and gastric secretory function in healthy volunteers.

AIM: To evaluate the short-term effects of rabeprazole 20 mg on endocrine parameters, in particular serum testosterone and cortisol, and on 24 h intragastric pH, H+ activity and nocturnal gastric acid secretion. METHODS: In this double-blind, two-period crossover study, 12 healthy young male volunteers were randomly given oral rabeprazole 20 mg o.m. or placebo for 14 days. There was a washout period of at least 1 week between the two studies. The effects of rabeprazole and placebo on cortisol and testosterone (primary criteria), and on tri-iodothyronine, thyroxine, 17beta-oestradiol, thyroid-stimulating hormone, thyroxine-binding protein, parathyroid hormone, insulin, glucagon, rennin, aldosterone, follicle-stimulating hormone, luteotrophic hormone, prolactin, somatotrophic hormone, dehydroepiandrosterone, cortisol-binding globulin and urinary 6-beta hydroxycortisol were compared. Intragastric 24 h pH, 24 h H+ activity and nocturnal gastric acid secretion were determined by pH probe and gastric aspiration. RESULTS: Rabeprazole produced no clinically relevant effects on endocrine function as assessed by measurement of serum testosterone, circadian serum cortisol levels, ACTH-stimulated serum cortisol levels and 17 other endocrine function tests. Rabeprazole significantly increased the 24 h median pH values compared to placebo (on Days 7 and 14 median values ranged from 3.92 to 6.88 with rabeprazole and from 1.48 and 4.22 with placebo, P < 0.001) and significantly decreased the integrated 24 h H+ activity (AUC08--08) from 343 mmol/L/h with placebo to 44 mmol/L/h with rabeprazole (P < 0.001). Following cessation of dosing, intragastric pH levels decreased and H+ activity increased, but acid secretion did not recover completely during the next 72 h. The mean value for nocturnal gastric acid secretion on Days 7 and 8 was 36 mmol/6 h with placebo and 5.6 mmol/6 h with rabeprazole (P < 0.001). Rabeprazole was well tolerated. CONCLUSION: Rabeprazole did not influence endocrine function in healthy young male volunteers during short-term dosing. Rabeprazole substantially increased intragastric pH over a 24 h period and significantly decreased intragastric acidity and nocturnal gastric acid secretion.

Human gastric acid secretion following repeated doses of AG-1749.

The effect of increasing doses (15 mg, 30 mg and 60 mg) of the substituted benzimidazole, AG-1749, on gastric acid secretion and fasting serum gastrin concentration has been studied after repeated administration to healthy volunteers. AG-1749 produced a dose-dependent and profound decrease in basal and stimulated gastric acid secretion in all volunteers, with almost total suppression at the highest dose. The extent of inhibition increased between Day 2 and Day 8 with the 15 and 30 mg doses of AG-1749. The inhibitory effect of AG-1749 appears to be fully reversible as control levels of acid output were reached 7 days after drug withdrawal. Seven days' dosing with 60 mg AG-1749 induced a more than threefold increment of fasting serum gastrin concentration, but this increase was still within the normal range. Seven days after cessation of dosing, fasting serum gastrin concentration returned to a pre-dose level.

Effects of pantoprazole on endocrine function in healthy male volunteers.

METHOD: In a randomized, double-blind, two-period crossover study, pantoprazole 40 mg or placebo were given orally to 12 male volunteers for 2 weeks each. There was a wash-out period of at least 1 week between the two treatment periods. The effects of pantoprazole or placebo on cortisol and testosterone (primary criteria), and tri-iodothyronine, thyroxine, thyroid-stimulating hormone, thyronine-binding protein, parathyroid hormone, insulin, glucagon, renin, aldosterone, follicle-stimulating hormone, luteotrophic hormone, prolactin and somatotrophic hormone were compared. In addition, intragastric 24-h pH, 24-h H(+)-activity, and volume of nocturnal gastric juice were determined by gastric aspiration technique. RESULTS: Pantoprazole did not influence plasma levels of testosterone, circadian cortisol concentrations or plasma cortisol levels after exogenous adrenocorticotropic hormone stimulation, as compared to placebo (P > 0.05, Koch's test). Furthermore, there were no clinically relevant changes with any of the other endocrine parameters. Pantoprazole significantly increased the median 24-h pH (group median 4.3 vs. 1.8; P < 0.001) and decreased 24-h H(+)-activity (4.0 vs. 22.6 mmol/L; P < 0.001). The volume of nocturnal gastric juice did not significantly differ between the two treatments. Pantoprazole was well tolerated and the frequency of adverse events was similar to placebo. No drug-related changes in laboratory values were observed. CONCLUSION: Pantoprazole did not influence endocrine function in healthy male volunteers during short-term treatment.

Lansoprazole versus omeprazole: influence on meal-stimulated gastric acid secretion.

AIMS: To investigate, by means of meal-stimulated acid secretion, the extent to which differences in plasma half-life, bioavailability and the recommended therapeutic dose can influence the antisecretory potency of lansoprazole and omeprazole. METHODS: In this double-blind, placebo-controlled, crossover study, 10 healthy male volunteers received 15 mg or 30 mg lansoprazole, 20 mg or 40 mg omeprazole or placebo for 5 days, in a randomized order. Meal-stimulated acid secretion was determined by means of a homogenized test meal and intragastric titration. RESULTS: On day 1, meal-stimulated acid secretion was decreased by 35% and 45% after administration of 15 mg or 30 mg lansoprazole, and by 16% and 42% after 20 mg or 40 mg omeprazole. After 3 and 5 days of dosing the decreases were 53% and 48% with 15 mg lansoprazole, 82% and 82% with 30 mg lansoprazole, 43% and 39% with 20 mg omeprazole, and 76% and 83% with 40 mg omeprazole. At all measuring points during the 5-day dosing periods, lansoprazole 15 mg and 30 mg proved superior to 20 mg omeprazole in inhibiting meal-stimulated gastric acid secretion, but the differences were only statistically significant for the lansoprazole 30 mg dose, 30 mg lansoprazole and 40 mg omeprazole proved equipotent. On day 1 only 30 mg lansoprazole was significantly better than placebo. CONCLUSION: This study demonstrated the following order of antisecretory potency: 30 mg lansoprazole = 40 mg omeprazole > 15 mg lansoprazole approximately 20 mg omeprazole.

What are the current possibilities in treating peptic ulcer disease?

There are two major principles of ulcer therapy. Today, the most widely accepted drugs are those which substantially reduce aggressive factors (i.c. acid and pepsin), namely histamine H2-receptor antagonists, antimuscarinics and antacids. Less frequently applied are mucoprotective agents like colloidal bismuth compounds and sucralfate. Prostaglandins both reduce acid secretion substantially and are believed to enhance mucosal resistance. Their anti-ulcer efficacy, however, is solely explicable by their antisecretory activity. Although mucosa-strengthening agents and H2-receptor blockers have nearly identical healing rates, mucosa-strengthening agents have inconvenient dosage regimens (four times or twice daily) and are probably less effective in relieving pain. The same holds true for antacids. Prostaglandins, antimuscarinics and antacids have dose related side effects. In contrast, H2-receptor blockers are characterized by a clear mechanism of action, convenient dosage regimens, good tolerance and a low incidence of side-effects. H2-receptor antagonists are the most effective anti-ulcer drugs presently available.

Dose-related healing of duodenal ulcer with the proton pump inhibitor lansoprazole.

Lansoprazole (AG 1749) is a novel substituted benzimidazole which inhibits gastric acid secretion by blocking H+,K(+)-ATPase. This randomized, double-blind multicentre trial studied the dose-response relationship of lansoprazole on ulcer healing and compared it with ranitidine in 314 out-patients with endoscopically assessed, symptomatic duodenal ulcer. Cumulative healing rates with Lansoprazole 7.5, 15, and 30 mg o.m. were 48, 59, and 74% at 2 weeks and 75, 84, and 95% at 4 weeks, respectively (intention-to-treat); the difference of the healing rates between 7.5 and 30 mg groups was significant (P less than 0.001). Corresponding healing rates for 300 mg ranitidine nocte were 51 and 89%. Pain relief was similar in all treatment groups. Lansoprazole was well tolerated. During a follow-up of 6 months relapse rates after lansoprazole 7.5, 15, and 30 mg were 21, 29, and 22%, respectively; the relapse rate after ranitidine 300 mg was 20%. In conclusion, lansoprazole provides faster healing of duodenal ulcer than ranitidine and a similar relapse pattern. For further trials in peptic ulcer disease a daily dose of lansoprazole 30 mg o.m. is recommended.

Effects of buffered and plain acetylsalicylic acid formulations with and without ascorbic acid on gastric mucosa in healthy subjects.

BACKGROUND: The most frequently reported adverse events associated with acetylsalicylic acid intake are minor gastrointestinal complaints. Galenic modifications, such as buffered formulations with or without ascorbic acid, may improve the benefit-risk ratio by decreasing the local mucosal side-effects of acetylsalicylic acid. AIM: To assess endoscopically-proven gastrointestinal lesions and the amount of gastric microbleeding of four different buffered and plain acetylsalicylic acid formulations, one containing paracetamol. METHODS: A randomized, four-fold cross-over study was performed in 17 healthy subjects who underwent serial oesophago-gastro-duodenoscopy before and after each course of 4-day dosing. Gastric aspirates were collected for the determination of haemoglobin concentrations to detect microbleeding. RESULTS: Buffered acetylsalicylic acid plus ascorbic acid yielded the lowest Lanza score, the lowest increase in the number of mucosal petechiae and the lowest increase in the amount of gastric microbleeding. Subjects receiving acetylsalicylic acid plus paracetamol plus caffeine showed the highest Lanza score of all treatments, and a considerably greater sum of petechiae in the oesophagus, stomach and duodenum compared with those receiving buffered acetylsalicylic acid plus ascorbic acid. CONCLUSIONS: The trial confirms that buffering of acetylsalicylic acid improves local gastric tolerability. Acetylsalicylic acid in combination with ascorbic acid shows significantly fewer gastric lesions and the lowest increase in gastric microbleeding compared with the other tested formulations.

The effects of lansoprazole, 30 or 60 mg daily, on intragastric pH and on endocrine function in healthy volunteers.

Seven days of dosing with either 30 mg or 60 mg of lansoprazole were compared with placebo in a double-blind, randomized, three-way cross-over study in 12 male healthy volunteers. Twenty-four-hour intragastric pH was measured after 7 days of dosing with each regimen, as well as 3 and 7 days after the end of dosing. During dosing with placebo, intragastric pH was above 4 for a median of 51 minutes. pH values were significantly raised to above 4 for 8.45 and 8.33 hours on Day 7 of dosing with lansoprazole 30 and 60 mg, respectively, but returned to normal by the third day after stopping dosing. No clinically relevant influence on endocrine function (serum concentrations of insulin, aldosterone, testosterone, parathormone, glucagon, T3, T4, TSH, LH, FSH, STH, prolactin, circadian cortisol profile, ACTH test) was observed. No serious adverse clinical or laboratory events were noted.

Nocturnal doses of ranitidine and nizatidine do not affect the disposition of diazepam.

The disposition of diazepam (D) after a single oral dose of 10 mg was evaluated in nine healthy male volunteers under the following conditions (randomized, double-blind, crossover design): D + comedication of placebo and D + nocturnal dosing with 300 mg ranitidine or 300 mg nizatidine. Plasma concentrations of D and its major active metabolite, desmethyldiazepam (DD), were monitored by a gas-liquid chromatography-electron-capture detection assay for 84 hours. Neither ranitidine nor nizatidine had any significant effect on the hepatic elimination of D as characterized by its terminal half-life (mean +/- SD) of 35.3 +/- 24.2 hours (+ ranitidine: 30.1 +/- 9.9 hr; + nizatidine: 37.3 +/- 18.3 hr) or total plasma clearance of 28.2 +/- 12.0 mL/min (+ ranitidine: 26.5 +/- 7.9 mL/min; + nizatidine: 26.7 +/- 10.4 mL/min). Likewise, the formation of DD as measured by its AUC was not affected by ranitidine or nizatidine. Thus, it can be concluded that concomitant once-daily dosing (300 mg nocturnally) with ranitidine or nizatidine does not impair hepatic drug metabolism.

Impact of ELISA and immunoblot as diagnostic tools one year after eradication of Helicobacter pylori in a multicentre treatment study.

The performance of serological tests for Helicobacter pylori infections is hampered by the persistence of antibodies after eradication therapy or spontaneous healing. Detection of different antigens or immunoglobulin classes might have an impact on the validity of serodiagnosis. The aim of this study was to assess the decrease in IgA and IgG antibody levels after eradication of H. pylori. Serum samples of 242 patients with active duodenal ulcer were tested with the ELISA and the immunoblot (IB) techniques for H. pylori-specific IgA and IgG antibodies before therapy and 1 year after successful eradication. From a total of 81 patients paired sera were available. At the end of the follow-up period ELISA antibody titres from the IgA class had decreased from a mean value of 6.69 to 4.26 units (P = 0.0001), and IgG class antibody titres from a mean value of 21.9 to 12.1 units (P = 0.0001). Regarding seroreversion, from 34 initially IgA positive sera 16 (47%), and from 74 IgG positive sera 18 (24%), had definitively reverted to 'negative'. One year after eradication, when tested with the immunoblot, the antibody responses against specific antigens of 37% IgA-positive sera (23/62) and 8% IgG-positive sera (6/78) reverted to 'negative', compared to a seroreversion rate of 27% of the anti-CagA IgA-positive sera (18/67) and of 9% of the anti-CagA IgG-positive sera (7/79). In conclusion, despite an overall significant decrease of H. pylori antibodies, both tests cannot be recommended for monitoring treatment success.

Pantoprazole versus omeprazole: influence on meal-stimulated gastric acid secretion.

AIMS: To determine the influence of recommended therapeutic doses of pantoprazole and omeprazole on meal-stimulated acid secretion. METHODS: In this double-blind, placebo-controlled, three-period crossover study, 12 healthy male volunteers received 40 mg pantoprazole od, 20 mg omeprazole od or placebo at 08:00 h for 5 days in a randomized order. Meal-stimulated acid secretion was determined by means of a homogenized test meal, and intragastric titration on day 1, 4-6 h, 8-10 h, 16-18 h, and 24-26 h, and on days 3 and 5, 4-6 h after oral drug administration. RESULTS: On day 1 (4-6 h after oral drug administration), meal-stimulated acid secretion was decreased by 36% and 24% after administration of 40 mg pantoprazole or 20 mg omeprazole, respectively. After 3 and 5 days of dosing, the decreases were 88% and 85% with 40 mg pantoprazole, and 70% and 74% with 20 mg omeprazole. At all measuring points during the 5-day dosing periods, 40 mg pantoprazole proved superior to 20 mg omeprazole in inhibiting meal-stimulated gastric acid secretion. The differences were statistically significant for pantoprazole on day 1, 24-26 h after oral drug administration and on day 3 (P = 0.0425 and P = 0.0244, respectively). On day 1, only pantoprazole was significantly better than placebo (P = 0.0210, 4-6 h after dosing; P = 0.0093, 8-10 h after dosing and P = 0.0068, 16-18 h after dosing). CONCLUSION: Pantoprazole 40 mg is significantly more effective than omeprazole 20 mg in inhibiting meal-stimulated acid secretion. In addition, pantoprazole exhibits a more rapid onset of action.

Effects of acetylsalicylic acid on ascorbic acid concentrations in plasma, gastric mucosa, gastric juice and urine--a double-blind study in healthy subjects.

OBJECTIVE: This study investigated concentrations of ascorbic acid (ASC) in gastric mucosa, gastric juice, urine and plasma in healthy subjects under steady state and fasted conditions with and without concomitant administration of acetylsalicylic acid (ASA). MATERIAL AND METHODS: This was a prospective, randomized, double-blind, parallel-group study in healthy subjects. It has assessed the effects of a 6-day administration of 0.8 g ASA or 0.48 g ASC, 3 times daily and the combination of both on concentrations of ASC in gastric mucosa, gastric juice, urine and plasma. Treatments were switched after 6 days without any washout for assessment of compartment sensitivity to changes in study medication resulting in an overall 14-day study period. Each of the 3 treatment groups consisted of 15 subjects. RESULTS: ASC concentrations were highest in the gastric mucosa (251+/-11 microg/g), followed by gastric juice (29+/-6 microg/ml), plasma (10+/-0.2 microg/ml), and urine (5+/-1 microg/ml). On day 7, ASC concentrations in gastric mucosa, plasma and urine had increased in those groups receiving ASC and decreased in the group receiving ASA only. All differences were statistically significant and indicate an interaction with ASA. In gastric juice, differences in ASC concentrations between the treatment groups were not statistically significant between baseline and day 7. ASC concentrations in plasma were strongly correlated with corresponding ASC concentrations in gastric mucosa (r = 0.34) and urine (r = 0.83), as were ASC concentrations in gastric mucosa with ASC in urine (r = 0.28). CONCLUSIONS: The gastric mucosa is the largest depot of ASC in the human body with ASC concentrations 25 times higher than in plasma. In healthy subjects, clinically relevant doses of ASA reduced ASC concentrations in gastric mucosa by about 10% within 6 days resulting from antioxidative defense mechanisms. In patients with long-term ASA treatment or conditions with additional risks such as elderly subjects with unfavorable dietary conditions and impaired antioxidative protection, a protective adjunct administration of ASC appears to be beneficial.