(1/694) Cimetidine transport in brush-border membrane vesicles from rat small intestine.
In previous studies, sulfoxide metabolite was observed in animal and human intestinal perfusions of cimetidine and other H2-antagonists. A sequence of follow-up studies is ongoing to assess the intestinal contributions of drug metabolism and drug and metabolite transport to variable drug absorption. An evaluation of these contributions to absorption variability is carried out in isolated fractions of the absorptive cells to uncouple the processes involved. In this report, data is presented on the drug entry step from a study on [3H]cimetidine uptake into isolated brush-border membrane vesicles from rat small intestine. A saturable component for cimetidine uptake was characterized with a Vmax and Km (mean +/- S.E.M.) of 6.1 +/- 1.5 nmol/30s/mg protein and 8.4 +/- 2.0 mM, respectively. Initial binding, and possibly intravesicular uptake, was inhibited by other cationic compounds including ranitidine, procainamide, imipramine, erythromycin, and cysteamine but not by TEA or by the organic anion, probenecid. Initial uptake was not inhibited by amino acids methionine, cysteine, or histidine, by the metabolite cimetidine sulfoxide, or by inhibitors of cimetidine sulfoxidation, methimazole, and diisothiocyanostilbene-2,2'-disulfonic acid. Equilibrium uptake was inhibited by ranitidine, procainamide, and cysteamine but not by erythromycin or imipramine. Initial cimetidine uptake was stimulated by an outwardly directed H+ gradient, and efflux was enhanced by an inwardly directed H+ gradient. Collapse of the H+ gradient as well as voltage-clamping potential difference to zero significantly reduced initial cimetidine uptake. The data is supportive of both a cimetidine/H+ exchange mechanism and a driving-force contribution from an inside negative proton or cation diffusion potential. (+info)
(2/694) Helicobacter pylori eradication with proton pump inhibitor-based triple therapies and re-treatment with ranitidine bismuth citrate-based triple therapy.
BACKGROUND: It has been suggested that short-term triple therapy comprising a proton pump inhibitor, plus clarithromycin and amoxycillin be used as first choice in treating H. pylori infection, while eradication failure patients should be further treated with a quadruple therapy. Nevertheless, conflicting results have been reported using these treatment regimens in different countries. METHODS: A total of 278 patients with H. pylori infection were randomised to receive one-week triple therapy, comprising clarithromycin 500 mg b.d., amoxycillin 1 g b.d., and either omeprazole 20 mg b.d. (OAC; 90 patients), or pantoprazole 40 mg b.d. (PAC; 95 patients), or lansoprazole 30 mg b.d. (LAC; 93 patients). H. pylori infection at entry, and eradication 4-6 weeks after therapy had ended, were assessed by rapid urease test and histology on biopsies from the antrum and the corpus. When eradication did not occur, patients were given a 2-week treatment comprising ranitidine bismuth citrate 400 mg b.d., tetracycline 500 mg t.d.s. and tinidazole 500 mg b.d. (RBTT). Eradication in these patients was assessed 4-6 weeks after conclusion of treatment by a further endoscopy. RESULTS: Six patients were lost to the follow-up. At the end of the first course of treatment, the overall H. pylori eradication rate was 78% (95% CI: 73-83) and 79% (95% CI: 75-84) at 'intention-to-treat' (ITT) and 'per protocol' (PP) analysis, respectively, without any statistically significant difference between treatment regimens, although a trend for better results with the omeprazole combination was observed. Moreover, H. pylori eradication was achieved in 82% (95% CI: 75-97) (ITT) and 86% (95% CI: 69-94) (PP) of 38 patients re-treated with RBTT regimen. CONCLUSIONS: Our data found that this short-term triple therapy is not a satisfactory treatment (< 80% eradication rate) for H. pylori infection. The 2-week triple therapy used as re-treatment in eradication failure patients yielded more promising results. (+info)
(3/694) Effect of Helicobacter pylori eradication on the natural history of duodenal ulcer disease.
BACKGROUND: Duodenal ulcer disease is strongly associated with Helicobacter pylori infection of the gastric mucosa. Eradication of H pylori from the gastric mucosa in adults is associated with long term healing of ulcers. AIMS: To follow a cohort of children with duodenal ulcer disease for a minimum of two years after the eradication of H pylori. PATIENTS AND METHODS: Over a three year period, all children diagnosed with duodenal ulcer disease had their symptoms documented and their H pylori status evaluated. The histories of these children were carefully screened to determine previous symptoms and to document previous treatment regimens. RESULTS: Sixteen children were diagnosed with ulcers and 15 were available for treatment and long term follow up. The median age at which symptoms first occurred was 10.5 years (range, 6-14) and the median duration of symptoms was 24 months (range, 2-60). Ten of the children had been treated with H2 receptor antagonists for a median of 3.5 months (range, 1-60). Duodenal ulcers healed in all children after eradication of H pylori and all children have remained asymptomatic for a median of 37 months (range, 26-62). No child has required subsequent admission to hospital. CONCLUSION: Eradication of H pylori is very effective in the long term healing of duodenal ulcer disease. H pylori eradication should be the standard treatment for all infected children who present with duodenal ulcer disease. (+info)
(4/694) An evaluation of increasing doses of ranitidine for treatment of heartburn.
BACKGROUND: This was a randomized, double-blind, placebo-controlled, multicentre, parallel group, dose-ranging trial of ranitidine tablets for relief of episodic heartburn. Adult out-patients who reported heartburn relieved by antacids at least seven times per week were eligible. METHODS: Patients who successfully completed a 1-week single-blind placebo run-in phase and who did not achieve adequate relief in more than 50% of heartburn episodes were randomized to a 1-week, double-blind treatment phase during which they received ranitidine doses of 25, 75 or 125 mg, or placebo. RESULTS: Of 577 patients randomized, 566 had at least one evaluable heartburn episode and were included in the intention-to-treat analysis. All three ranitidine doses were statistically significantly superior to placebo in providing overall episodic heartburn relief for the first episode (P < 0.002), last episode (P=0.004), and all episodes combined (P < 0.001). The ranitidine 75 mg and 125 mg doses provided sustained relief (relief within 60 min of dosing that lasted throughout the 4-h evaluation period) to a greater proportion of patients for each individual episode (43-56% for 75 mg and 42-57% for 125 mg) than the ranitidine 25 mg dose (35-50%) or placebo (21-29%). The incidence of adverse events was similar in all treatment groups. CONCLUSIONS: All three ranitidine doses (125, 75 and 25 mg) are safe and superior to placebo in providing adequate relief for heartburn. Ranitidine's onset of relief was progressive and clearly present by 30 min as shown by statistically significant differences for the 75 mg dose when compared to placebo. Similarly, patients treated with ranitidine 75 mg and 125 mg consumed statistically fewer rescue antacids than placebo-treated patients for the first episode. All three doses were well tolerated, with adverse event profiles similar to those of placebo. (+info)
(5/694) Effect of histamine H2-receptor antagonist on the phosphorus-binding abilities of calcium carbonate and calcium lactate in hemodialysis patients.
The effect of histamine H2-receptor antagonist (famotidine) on the phosphorus-binding abilities of calcium carbonate and calcium lactate were examined in 13 chronic hemodialysis patients. In seven patients receiving calcium carbonate, famotidine (20 mg/d) was given because of gastroduodenal disorders, and calcium carbonate was replaced with calcium lactate as a phosphorus binder after 4 wk of treatment with famotidine. With the 4-wk administration of famotidine accompanied by calcium carbonate, the serum phosphorus level increased from 6.3+/-0.9 to 7.1+/-0.5 mg/dl (P<0.05). However, with the substitution of calcium lactate, the serum phosphorus level decreased significantly when compared to that before substitution (6.3+/-0.2 and 6.0+/-0.9 mg/dl after 4 and 8 wk of substitution, respectively), despite continued administration of famotidine. Serum calcium, creatinine, alkaline phosphatase, high sensitive parathyroid hormone, blood urea nitrogen, arterial blood pH, and bicarbonate were not significantly altered during the trial period. In six control patients treated with calcium carbonate alone, there were no statistical changes in serum calcium and phosphorus levels after substitution of calcium lactate for calcium carbonate. These results suggest that famotidine significantly affects the phosphorus-binding ability of calcium carbonate, but not that of calcium lactate. A careful observation of changes in the serum phosphorus level should be required in hemodialysis patients receiving calcium carbonate and histamine H2-receptor antagonists. Calcium lactate may be useful as a phosphorus binder in such hemodialysis patients. (+info)
(6/694) Alcohol-histamine interactions.
Alcohol and histamine metabolic pathways in the body have the common enzymes aldehyde dehydrogenase and aldehyde oxidase. The metabolite of ethanol, acetaldehyde, can effectively compete with the metabolites of histamine, methylimidazole acetaldehyde, and imidazole acetaldehyde. At the periphery, alcohol and acetaldehyde liberate histamine from its store in mast cells and depress histamine elimination by inhibiting diamine oxidase, resulting in elevated histamine levels in tissues. Histamine mediates alcohol-induced gastric and intestinal damage and bronchial asthma as well as flushing in Orientals. On the other hand, alcohol provokes food-induced histaminosis and histamine intolerance, which is an epidemiological problem. There are many controversial reports concerning the effect of H2 receptor antagonists on ethanol metabolism and the activity of alcohol dehydrogenase in the stomach. In addition, alcohol affects histamine levels in the brain by modulating histamine synthesis, release, and turnover. Histamine receptor antagonists can affect ethanol metabolism and change the sensitivity of animals to the hypnotic effects of alcohol. In contrast to other neurotransmitters, the involvement of the brain histamine system in the mechanisms of the central actions of alcohol and in the pathogenesis of alcoholism is poorly studied and understood. (+info)
(7/694) L-365,260 inhibits in vitro acid secretion by interacting with a PKA pathway.
The aim of this study was to analyse the antisecretory mechanism of L-365,260 in vitro in isolated rabbit gastric glands. We showed that compound L-365,260, described as a non-peptide specific competitive CCK-B receptor antagonist, was able to dose-dependently inhibit [14C]-aminopyrine accumulation induced by histamine (10(-4) M), carbachol (5x10(-5) M), 3-isobutyl-1-methyl-xanthine (IBMX) (5x10(-6) M) and forskolin (5x10(-7) M) with similar IC50 values respectively of 1.1+/-0.6x10(-7) M, 1.9+/-1.2x10(-7) M, 4.2+/-2.0x10(-7) M and 4.0+/-2.8x10(-7) M. We showed that L-365,260 acted beyond receptor activation and production of intracellular second messengers and that it had no action on the H+/K+ -ATPase. We found that L-365,260 inhibited cyclic AMP-induced [14C]-aminopyrine accumulation in digitonin-permeabilized rabbit gastric glands, suggesting that this compound acted, at least in part, as an inhibitor of the cyclic AMP-dependent protein kinase (PKA) pathway. (+info)
(8/694) Efficacy of omeprazole versus ranitidine for symptomatic treatment of poorly responsive acid reflux disease-a prospective, controlled trial.
BACKGROUND: H2-receptor antagonists are widely used in patients with gastro-oesophageal reflux disease (GERD) and are frequently continued when symptoms persist. AIM: To compare the efficacy of omeprazole 20 mg once daily with that of ranitidine 150 mg twice daily in relieving GERD symptoms, in patients who remained symptomatic following a 6-week course of ranitidine therapy. METHODS: Patients with heartburn on at least 4 days/week but who did not have endoscopy to assess oesophageal mucosa could participate. This two-phase, prospective trial included a 6-week open-label phase (phase I), followed by an 8-week double-blind phase (phase II). Patients still symptomatic following treatment with ranitidine 150 mg twice daily (phase I) were randomized to double-blind treatment (phase II) with either omeprazole 20 mg once daily or ranitidine 150 mg twice daily. The primary efficacy variable was the proportion of patients with heartburn resolution during weeks 4 and 8 of phase II. RESULTS: Of the 533 patients with GERD who received ranitidine in phase I, 348 patients (65%) were still symptomatic. A total of 317 patients (59%) were randomized to double-blind treatment (phase II). At week 8, a significantly (P < 0.0004) greater proportion of omeprazole-treated patients (70%) experienced no more than mild heartburn compared with ranitidine-treated patients (49%). Complete resolution of heartburn also occurred in a significantly (P < 0. 00001) greater proportion of omeprazole-treated patients (46% vs. 16% of the ranitidine group at week 8). CONCLUSIONS: After 6 weeks of ranitidine treatment, the majority of patients with GERD were still experiencing moderate to severe heartburn. Omeprazole was significantly more effective than ranitidine in resolving heartburn in this group of patients. (+info)