Acid suppression in peptic ulcer haemorrhage: a 'meta-analysis'.
(57/694)
BACKGROUND: The use of acid-decreasing agents in the management of peptic ulcer haemorrhage continues to be controversial. Most clinical trials examining the efficacy of these drugs contain small numbers of patients, making it difficult to draw conclusions about their efficacy. METHODS: We report a meta-analysis that examined the effect of these drugs in the management of peptic ulcer haemorrhage. Included studies were located using a search of the Medline database between 1980 and 1999. Studies were published in English, randomized and controlled by a placebo group. Mantel-Haenszel and blinded random models were used in conducting the statistical processing of this meta-analysis. RESULTS: Twenty-one randomized placebo-controlled trials were included. The total number of patients was 3566 and the mean study size was 170 (range 20-1005). Seventeen of the papers assessed the efficacy of H2-antagonists, three assessed proton pump inhibitors and one was concerned with antacid therapy. The meta-analysis showed a significant reduction in re-bleeding rates (odds ratio, OR 0.727, 0.618-0.855, P < 0.001) and surgery rates (OR 0.707, 0.582-0.859, P < 0.001) when acid decreasing agents are used for acute peptic ulcer haemorrhage. Mortality rates appear to be unaffected (OR 1.140, 0.818-1.588, P=0. 49). CONCLUSIONS: This meta-analysis demonstrates a significant beneficial effect of acid-decreasing agents in lowering re-bleeding and surgery rates, but demonstrated no effect upon mortality. (+info)
BACKGROUND: The most widely used treatments for ulcer healing and Helicobacter pylori eradication consist of a 1-2 week regimen of a proton pump inhibitor plus two or three antimicrobials. AIMS: To evaluate the efficacy, safety, cost, and tolerance of a three-day regimen with three antibiotics vs. a 10-day treatment with a proton pump inhibitor or vs. a ranitidine bismuth citrate triple therapy. METHODS: Two hundred and twenty-one patients with endoscopically-proven H. pylori-positive duodenal ulcers were recruited to the study. Recruited patients were assigned to one of the following four regimens: (I) omeprazole 40 mg o.m. plus amoxycillin 1 g b.d. and clarithromycin 500 mg b.d. for 10 days (OAC: 55 patients); (ii) omeprazole 40 mg o.m. on days 1-5, plus amoxycillin 1 g b.d., clarithromycin 500 mg b.d. and metronidazole 500 mg b.d. on days 3-5 (OACM: 56 patients); (iii) ranitidine bismuth citrate 400 mg b.d. plus amoxycillin 1 g b.d. and clarithromycin 500 mg b.d. for 10 days (RAC: 54 patients); (iv) ranitidine bismuth citrate 400 mg b.d. on days 1-5, plus amoxycillin 1 g b.d., clarithromycin 500 mg b.d. and metronidazole 500 mg b.d. on days 3-5 (RACM: 56 patients). Fisher's exact test was used to compare data regarding healing and eradication in the four groups. RESULTS: The intention-to-treat eradication and ulcer healing rates for the RACM regimen were 95% and 98%, respectively. Statistically significant differences were observed, relating to the eradication and healing of ulcers, between RACM and either the RAC or OAC regimens. CONCLUSION: The three-day antibiotic therapy with amoxycillin, clarithromycin and metronidazole in addition to ranitidine bismuth citrate is a very effective anti-H. pylori regimen. (+info)
Regulation of parietal cell calcium signaling in gastric glands.
(59/694)
The ligands interacting with enterochromaffin-like (ECL) and parietal cells and the signaling interactions between these cells were investigated in rabbit gastric glands using confocal microscopy. Intracellular calcium concentration ([Ca(2+)](i)) changes were used to monitor cellular responses. Histamine and carbachol increased [Ca(2+)](i) in parietal cells. Gastrin (1 nM) increased [Ca(2+)](i) in ECL cells and adjacent parietal cells. Only the increase of [Ca(2+)](i) in parietal cells was inhibited by H(2) receptor antagonists (H(2)RA). Gastrin (10 nM) evoked an H(2)RA-insensitive [Ca(2+)](i) increase in parietal cells. Carbachol produced large H(2)RA- and somatostatin-insensitive signals in parietal cells. Pituitary adenylate cyclase-activating peptide (PACAP, 100 nM) elevated [Ca(2+)](i) in ECL cells and adjacent parietal cells. H(2)RAs abolished the PACAP-stimulated [Ca(2+)](i) increase in adjacent parietal cells. Somatostatin did not inhibit the increase of [Ca(2+)](i) in parietal cells stimulated with histamine, high gastrin concentrations, or carbachol but abolished ECL cell calcium responses to gastrin or PACAP. Hence, rabbit parietal cells express histaminergic, muscarinic, and CCK-B receptors coupled to calcium signaling but insensitive to somatostatin, whereas rabbit and rat ECL cells express PACAP and CCK-B calcium coupled receptors sensitive to somatostatin. (+info)
Cimetidine (Tagamet) is a reproductive toxicant in male rats affecting peritubular cells.
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Cimetidine (Tagamet) is a potent histaminic H2-receptor antagonist, extensively prescribed for ulcers and now available without prescription. Cimetidine is a known testicular toxicant, but its mechanism of action remains uncertain. Rats were treated i.p. with cimetidine either at 50 mg/kg or 250 mg/kg body weight for 59 days. Accessory sex organ weights, but not testis weight, were significantly reduced in the high dose treated groups. FSH levels were significantly elevated in both treated groups, but testosterone levels were unchanged. A high degree of variability characterized testis histology, with most tubules appearing normal and some tubules (15-17%) partially lacking or devoid of germ cells. Morphometry showed that although seminiferous tubule volume was not significantly changed, the volume of peritubular tissue was reduced in the high dose group. There was extensive duplication of the basal lamina, lamina densa in both apparently normal spermatogenic tubules and severely damaged tubules. Apoptotic peritubular myoid cells were also found. TUNEL labeling confirmed extensive apoptotic cell death in peritubular cells, but revealed apoptosis of vascular smooth muscle. Given that 1) peritubular myoid cell apoptosis occurs in apparently normal tubules, that 2) basal lamina disorders are found, and that 3) peritubular cells are lost from the testis, it is suggested that the primary event in cimetidine-related damage is targeted to testicular smooth muscle cells. This is the first in vivo-administered toxicant to be described that targets myoid cells, resulting in abnormal spermatogenesis. (+info)
Dehydration-induced vasopressin secretion in humans: involvement of the histaminergic system.
(61/694)
In rats, the hypothalamic neurotransmitter histamine participates in regulation of vasopressin secretion and seems to be of physiological importance, because blockade of the histaminergic system reduces dehydration-induced vasopressin secretion. We investigated whether histamine is also involved in regulation of vasopressin secretion during dehydration in humans. We found that 40 h of dehydration gradually increased plasma osmolality by 10 mosmol/kg and induced a fourfold increase in vasopressin levels. Pretreatment with the H(2)-receptor antagonists cimetidine or ranitidine significantly reduced the dehydration-induced increase in vasopressin levels approximately 40% after 34 and 37 h of dehydration, whereas this was not the case with the H(1)-receptor antagonist mepyramine. Dehydration reduced aldosterone secretion by approximately 50%. This effect of dehydration was reduced by both H(1)- and H(2)-receptor blockade after 16 and/or 34 h of dehydration. We conclude that vasopressin secretion in response to dehydration in humans is under the regulatory influence of histamine and that the effect seems to be mediated via H(2)-receptors. In addition, the regulation of aldosterone secretion during dehydration also seems to involve the histaminergic system via H(1) and H(2) receptors. (+info)
Oxidation of ranitidine by isozymes of flavin-containing monooxygenase and cytochrome P450.
(62/694)
Rat and human liver microsomes oxidized ranitidine to its N-oxide (66-76%) and S-oxide (13-18%) and desmethylranitidine (12-16%). N- and S-oxidations of ranitidine were inhibited by metimazole [flavin-containing monooxygenase (FMO) inhibitor] to 96-97% and 71-85%, respectively, and desmethylation of ranitidine was inhibited by SKF525A [cytochrome P450 (CYP) inhibitor] by 71-95%. Recombinant FMO isozymes like FMO1, FMO2, FMO3 and FMO5 produced 39, 79, 2180 and 4 ranitinine N-oxide and 45, 0, 580 and 280 ranitinine S-oxide pmol x min(-1) x nmol(-1) FMO, respectively. Desmethyranitinine was not produced by recombinant FMOs. Production of desmethylranitidine by rat and human liver microsomes was inhibited by tranylcypromine, a-naphthoflavon and quinidine, which are known to inhibit CYP2C19, 1A2 and 2D6, repectively. FMO3, the major form in adult liver, produced both ranitidine N- and S-oxides at a 4 to 1 ratio. FMO1, expressed primarily in human kidney, was 55- and 13-fold less efficient than the hepatic FMO3 in producing ranitidine N- and S-oxides, respectively. FMO2 and FMO5, although expressed slightly in human liver, kidney and lung, were not efficient producers of ranitidine N- and S-oxides. Thus, urinary contents of ranitidine N-oxide can be used as the in vivo probe to determine the hepatic FMO3 activity. (+info)
Evaluation of the pharmacokinetics and electrocardiographic pharmacodynamics of loratadine with concomitant administration of ketoconazole or cimetidine.
(63/694)
AIMS: To evaluate whether ketoconazole or cimetidine alter the pharmacokinetics of loratadine, or its major metabolite, desloratadine (DCL), or alter the effects of loratadine or DCL on electrocardiographic repolarization in healthy adult volunteers. METHODS: Two randomized, evaluator-blind, multiple-dose, three-way crossover drug interaction studies were performed. In each study, subjects received three 10 day treatments in random sequence, separated by a 14 day washout period. The treatments were loratadine alone, cimetidine or ketoconazole alone, or loratadine plus cimetidine or ketoconazole. The primary study endpoint was the difference in mean QTc intervals from baseline to day 10. In addition, plasma concentrations of loratadine, DCL, and ketoconazole or cimetidine were obtained on day 10. RESULTS: Concomitant administration of loratadine and ketoconazole significantly increased the loratadine plasma concentrations (307%; 90% CI 205-428%) and DCL concentrations (73%; 62-85%) compared with administration of loratadine alone. Concomitant administration of loratadine and cimetidine significantly increased the loratadine plasma concentrations (103% increase; 70-142%) but not DCL concentrations (6% increase; 1-11%) compared with administration of loratadine alone. Cimetidine or ketoconazole plasma concentrations were unaffected by coadministration with loratadine. Despite increased concentrations of loratadine and DCL, there were no statistically significant differences for the primary electrocardiographic repolarization parameter (QTc) among any of the treatment groups. No other clinically relevant changes in the safety profile of loratadine were observed as assessed by electrocardiographic parameters (mean (90% CI) QTc changes: loratadine vs loratadine + ketoconazole = 3.6 ms (-2.2, 9.4); loratadine vs loratadine + cimetidine = 3.2 ms (-1.6, 7.9)), clinical laboratory tests, vital signs, and adverse events. CONCLUSIONS: Loratadine 10 mg daily was devoid of any effects on electrocardiographic parameters when coadministered for 10 days with therapeutic doses of ketoconazole or cimetidine in healthy volunteers. It is concluded that, although there was a significant pharmacokinetic drug interaction between ketoconazole or cimetidine and loratadine, this effect was not accompanied by a change in the QTc interval in healthy adult volunteers. (+info)
Study of interaction of gastroenterological agents in the presence of cytoprotective drugs. Part I: Adsorption of the chosen inhibitors of histamine H2 receptors on sucralfat in vitro.
(64/694)
We investigated adsorption of the chosen histamine H2 receptor inhibitors on sucralfat. Evaluation of adsorption was conducted by statistic methods in vitro taking into account environment reaction and sucralfat form. The obtained results prove that the tested therapeutic substances are adsorbed on sucralfat in all used pH ranges and the ability of sucralfat bounding depends on its form and environment reaction. The highest adsorption value was observed in the samples with pH 3.6 in the presence of sucralfat suspension, and the lowest in environment pH 1.5 in the presence of sucralfat paste. From among the tested histamine receptors ranitidine hydrochloride is adsorbed in the best way and cimetidine hydrochloride and famotidine in much worse way. (+info)