Development and in vitro/in vivo evaluation of famotidine hydrochloride bioadhesive sustained release suspension

To develop a new kind of famotidine-resin microcapsule for gastric adhesion sustained release by screening out suitable excipients and designing reasonable prescriptions to improve patient drug activities to achieve the expected therapeutic effect. The famotidine drug resin was prepared using the water bath method with carbomer 934 used as coating material. Microcapsules were prepared using the emulsified solvent coating method and appropriate excipients were used to prepare famotidine sustained release suspension. Pharmacokinetics of the developed microcapsules were studied in the gastrointestinal tract of rats. The self-made sustained-release suspension of famotidine hydrochloride effectively reduced the blood concentration and prolonged the action time. The relative bioavailability of the self-made suspension of the famotidine hydrochloride to the commercially available famotidine hydrochloride was 146.44%, with an average retention time of about 5h longer, which indicated that the new suspension had acceptable adhesion properties. The findings showed that the newly developed famotidine-resin microcapsule increased the bioavailability of the drug with a significant sustained-release property.

Effects of taxifolin on aspirin-induced gastric damage in rats: macroscopic and biochemical evaluation

Taxifolin (dihydroquercetin) is a flavanonol isolated from various plants and has antioxidant effects. The aim of our study was to macroscopically and biochemically investigate the effects of taxifolin on aspirin-induced oxidative gastric damage in rats and to evaluate them by comparison with those of famotidine. Rats were divided into four drug administration groups: a healthy control group, an aspirin-only group (ASG), a taxifolin + aspirin group (TASG), and a famotidine + aspirin group (FASG). The results revealed that in light of the results that we obtained, 50 mg/kg taxifolin had anti-ulcer effects. At this dose, taxifolin was able to bring COX-1 activities to a level close to those seen in healthy rats with appropriate macroscopic, oxidant/antioxidant, and biochemical parameters. Based on these results, it can be said that taxifolin may be successfully used as a more potent alternative to famotidine, which is the currently accepted treatment for aspirin-induced ulcers.

Comparison of the acid suppression effects between low-dose esomeprazole and famotidine in healthy subjects

OBJECTIVE

Famotidine, an H2 receptor antagonist (H2RA), is mainly prescribed to alleviate the early symptoms of gastritis. Our aim was to explore the possibilities of low-dose esomeprazole as a treatment of gastritis as well as the pharmacodynamic (PD) properties of esomeprazole and famotidine.

MATERIALS AND METHODS

A randomized, multiple-dose, 6-sequence, 3-period crossover study was conducted with a 7-day washout between periods. For each period, the subjects were administered one dose of esomeprazole 10 mg or famotidine 20 mg or esomeprazole 20 mg each day. To evaluate the PDs, the 24-hour gastric pH was recorded after single and multiple doses. The mean percentage of time during which the gastric pH was above 4 was evaluated for PD assessment. To confirm the pharmacokinetic (PK) characteristics of esomeprazole, blood was collected for up to 24 hours after multiple doses.

RESULTS

26 subjects completed the study. Following the multiple doses of esomeprazole 10 mg, esomeprazole 20 mg, and famotidine 20 mg, the mean percentages of time during which the gastric pH was above 4 over the course of 24 hour were 35.77 ± 19.56%, 53.75 ± 20.55%, and 24.48 ± 17.36%, respectively. After multiple doses, the time of peak plasma concentration at steady state (tmax,ss) was 1.00 and 1.25 hours for 10 and 20 mg of esomeprazole, respectively. The geometric mean ratio and its 90% confidence interval of area under the plasma drug concentration-time curve in steady state (AUCT,ss) and maximum concentration of drug in plasma in steady state (Cmax,ss) for esomeprazole 10 mg compared to 20 mg were 0.3654 (0.3381 - 0.3948) and 0.5066 (0.4601 - 0.5579), respectively.

CONCLUSION

The PD parameters of esomeprazole 10 mg were comparable to those of famotidine after multiple doses. These findings provide support for further evaluating the use of 10 mg of esomeprazole as a treatment option for gastritis.

Esomeprazole induces structural changes and apoptosis and alters function of in vitro canine neoplastic mast cells

Histamine-2 receptor antagonists such as famotidine and proton pump inhibitors such as esomeprazole are commonly used in canine MCT disease, but direct effects on dog MCs have not been evaluated. Omeprazole is a proton pump inhibitor which has been demonstrated to cause structural and functional changes to in vitro murine mast cells (MCs). It has not yet been determined if esomeprazole, the commercially available and commonly prescribed S-isomer of omeprazole, has similar effects. Our primary study objective was to evaluate and compare the effects of acid suppressants (esomeprazole and famotidine) on MC ultrastructure, viability, and function in vitro using both healthy and neoplastic MCs. Murine bone marrow derived mast cells (BMMC), human LAD2, and canine C2 and BR cells, were used for these studies, representing a single healthy (i.e., BMMCs) MC model and multiple neoplastic MC models (i.e., LAD2, C2, BR), respectively. The rat basophilic leukemic (RBL-2H3) and canine B cell lymphoma 17-71 cell lines served as granulocytic and agranulocytic control lines for experiments, respectively. The treatment effect of acid suppressants on MC ultrastructure was assessed via both light and transmission electron microscopy. Differences in MC viability was assessed between groups via MTS-based, colorimetric assays and flow cytometry. Degranulation was assessed by quantification of β-hexosaminidase (i.e., LAD2 and RBL-2H3). Esomeprazole-treated MCs of all lines exhibited dramatic time and concentration-dependent alterations in ultrastructure (i.e., increased vacuolization, compromise of cell membrane), increased apoptosis, and altered degranulation responses in comparison to famotidine and vehicle-treated cells. The canine B cell lymphoma cells consistently exhibited either no significant (i.e., cytotoxicity assays) or greatly diminished treatment responses (i.e., apoptosis) compared to MCs. Esomeprazole, but not famotidine, induces significant cytotoxicity, as well as alterations to cell structure and function to multiple lines of in vitro neoplastic MCs. Continued in vitro work investigating the specific mechanisms by which proton pump inhibitors induce these effects, as well as prospective, in vivo work comparing the treatment effects of acid suppressants on canine MCTs, are warranted.

Hypolipemic effects of histamine is due to inhibition of VLDL secretion from the liver: involvement of both H1 and H2-receptors

The research was performed to study the mechanism whereby histamine affects the profile of plasma lipids. Six groups of ten male rats were received two injections with histamine or its H1- and H2-agonists and antagonists. Histamine caused a significant decrease in the concentrations of triglyceride, total cholesterol, and LDLc, while HDLc had no significant change. The rate of VLDL secretion was 263.6 ± 25.8 mg/h dL in control rats and was inhibited by about 68% in histamine injected rats. These changes have been mimicked by either histamine H1- or H2-agonists. The effects of H1- and H2-agonists were abolished in the presence of cetirizine and famotidine respectively. Histamine causes a significant decrease in serum triglyceride, total, and LDL-cholesterol by both H1 and H2-receptors. The decrease in serum lipids is due to the inhibitory effect of histamine or its agonists on VLDL secretion from the liver.

Molecular basis for the repurposing of histamine H2-receptor antagonist to treat COVID-19

With the world threatened by a second surge in the number of Coronavirus cases, there is an urgent need for the development of effective treatment for the novel coronavirus (COVID-19). Recently, global attention has turned to preliminary reports on the promising anti-COVID-19 effect of histamine H2-receptor antagonists (H2RAs), most especially Famotidine. Therefore, this study was designed to exploit a possible molecular basis for the efficacy of H2RAs against coronavirus. Molecular docking was performed between four H2RAs, Cimetidine, Famotidine, Nizatidine, Ranitidine, and three non-structural proteins viz. NSP3, NSP7/8 complex, and NSP9. Thereafter, a 100 ns molecular dynamics simulation was carried out with the most outstanding ligands to determine the stability. Thereafter, Famotidine and Cimetidine were subjected to gene target prediction analysis using HitPickV2 and eXpression2Kinases server to determine the possible network of genes associated with their anti-COVID activities. Results obtained from molecular docking showed the superiority of Famotidine and Cimetidine compared to other H2RAs with a higher binding affinity to all selected targets. Molecular dynamic simulation and MMPBSA results revealed that Famotidine as well as Cimetidine bind to non-structural proteins more efficiently with high stability over 100 ns. Results obtained suggest that Famotidine and Cimetidine could be a viable option to treat COVID-19 with a mechanism of action that involves the inhibition of viral replication through the inhibition of non-structural proteins. Therefore, Famotidineand Cimetidine qualify for further study as a potential treatment for COVID-19.

Famotidine activates the vagus nerve inflammatory reflex to attenuate cytokine storm

BACKGROUND

Severe COVID-19 is characterized by pro-inflammatory cytokine release syndrome (cytokine storm) which causes high morbidity and mortality. Recent observational and clinical studies suggest famotidine, a histamine 2 receptor (H2R) antagonist widely used to treat gastroesophageal reflux disease, attenuates the clinical course of COVID-19. Because evidence is lacking for a direct antiviral activity of famotidine, a proposed mechanism of action is blocking the effects of histamine released by mast cells. Here we hypothesized that famotidine activates the inflammatory reflex, a brain-integrated vagus nerve mechanism which inhibits inflammation via alpha 7 nicotinic acetylcholine receptor (α7nAChR) signal transduction, to prevent cytokine storm.

METHODS

The potential anti-inflammatory effects of famotidine and other H2R antagonists were assessed in mice exposed to lipopolysaccharide (LPS)-induced cytokine storm. As the inflammatory reflex is integrated and can be stimulated in the brain, and H2R antagonists penetrate the blood brain barrier poorly, famotidine was administered by intracerebroventricular (ICV) or intraperitoneal (IP) routes.

RESULTS

Famotidine administered IP significantly reduced serum and splenic LPS-stimulated tumor necrosis factor (TNF) and IL-6 concentrations, significantly improving survival. The effects of ICV famotidine were significantly more potent as compared to the peripheral route. Mice lacking mast cells by genetic deletion also responded to famotidine, indicating the anti-inflammatory effects are not mast cell-dependent. Either bilateral sub-diaphragmatic vagotomy or genetic knock-out of α7nAChR abolished the anti-inflammatory effects of famotidine, indicating the inflammatory reflex as famotidine's mechanism of action. While the structurally similar H2R antagonist tiotidine displayed equivalent anti-inflammatory activity, the H2R antagonists cimetidine or ranitidine were ineffective even at very high dosages.

CONCLUSIONS

These observations reveal a previously unidentified vagus nerve-dependent anti-inflammatory effect of famotidine in the setting of cytokine storm which is not replicated by high dosages of other H2R antagonists in clinical use. Because famotidine is more potent when administered intrathecally, these findings are also consistent with a primarily central nervous system mechanism of action.

Immunomodulatory agents for COVID-19 treatment: possible mechanism of action and immunopathology features

The novel coronavirus pandemic has emerged as one of the significant medical-health challenges of the current century. The World Health Organization has named this new virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the first detection of SARS-CoV-2 in November 2019 in Wuhan, China, physicians, researchers, and others have made it their top priority to find drugs and cures that can effectively treat patients and reduce mortality rates. The symptoms of Coronavirus Disease 2019 (COVID-19) include fever, dry cough, body aches, and anosmia. Various therapeutic compounds have been investigated and applied to mitigate the symptoms in COVID-19 patients and cure the disease. Degenerative virus analyses of the infection incidence and COVID-19 have demonstrated that SARS-CoV-2 penetrates the pulmonary alveoli's endothelial cells through Angiotensin-Converting Enzyme 2 (ACE2) receptors on the membrane, stimulates various signaling pathways and causes excessive secretion of cytokines. The continuous triggering of the innate and acquired immune system, as well as the overproduction of pro-inflammatory factors, cause a severe condition in the COVID-19 patients, which is called "cytokine storm". It can lead to acute respiratory distress syndrome (ARDS) in critical patients. Severe and critical COVID-19 cases demand oxygen therapy and mechanical ventilator support. Various drugs, including immunomodulatory and immunosuppressive agents (e.g., monoclonal antibodies (mAbs) and interleukin antagonists) have been utilized in clinical trials. However, the studies and clinical trials have documented diverging findings, which seem to be due to the differences in these drugs' possible mechanisms of action. These drugs' mechanism of action generally includes suppressing or modulating the immune system, preventing the development of cytokine storm via various signaling pathways, and enhancing the blood vessels' diameter in the lungs. In this review article, multiple medications from different drug families are discussed, and their possible mechanisms of action are also described.

Famotidine inhibits toll-like receptor 3-mediated inflammatory signaling in SARS-CoV-2 infection

Apart from prevention using vaccinations, the management options for COVID-19 remain limited. In retrospective cohort studies, use of famotidine, a specific oral H2 receptor antagonist (antihistamine), has been associated with reduced risk of intubation and death in patients hospitalized with COVID-19. In a case series, nonhospitalized patients with COVID-19 experienced rapid symptom resolution after taking famotidine, but the molecular basis of these observations remains elusive. Here we show using biochemical, cellular, and functional assays that famotidine has no effect on viral replication or viral protease activity. However, famotidine can affect histamine-induced signaling processes in infected Caco2 cells. Specifically, famotidine treatment inhibits histamine-induced expression of Toll-like receptor 3 (TLR3) in SARS-CoV-2 infected cells and can reduce TLR3-dependent signaling processes that culminate in activation of IRF3 and the NF-κB pathway, subsequently controlling antiviral and inflammatory responses. SARS-CoV-2-infected cells treated with famotidine demonstrate reduced expression levels of the inflammatory mediators CCL-2 and IL6, drivers of the cytokine release syndrome that precipitates poor outcome for patients with COVID-19. Given that pharmacokinetic studies indicate that famotidine can reach concentrations in blood that suffice to antagonize histamine H2 receptors expressed in mast cells, neutrophils, and eosinophils, these observations explain how famotidine may contribute to the reduced histamine-induced inflammation and cytokine release, thereby improving the outcome for patients with COVID-19.

Marine Bacterial Compounds Evaluated by In Silico Studies as Antipsychotic Drugs Against Schizophrenia

Schizophrenia (SCZ) is one of the brain disorders which affects the thinking and behavioral skills of patients. This disorder comes along with an overproduction of kynurenic acid in the cerebrospinal fluid and the prefrontal cortex of SCZ patients. In this study, marine bacterial compounds were screened for their suitability as antagonists against human kynurenine aminotransferase (hKAT-1) which causes the synthesis of kynurenic acid downstream which ultimately causes the SCZ disorder according to the kynurenic hypothesis of SCZ. The marine actinobacterial compound bonactin shows more promising results than other tested marine compounds such as the histamine H2 blocker famotidine and indole-3-acetic acid (IAC) from docking and in silico toxicological studies carried out here. The obtained results of the Grid-based Ligand Docking with Energetics (Glide) scores of extra-precision (XP) Glide against the target protein hKAT-1 on IAC, famotidine, and bonactin were - 6.581, - 6.500 and - 7.730 kcal/mol where Glide energies were - 29.84, - 28.391, and - 47.565 kcal/mol, respectively. Bonactin is known as an antibacterial and antifungal compound being extracted from a marine Streptomyces sp. Comparing tested compounds against the drug target hKAT-1, bonactin alone showed the best Glide score and Glide energy on the target protein hKAT-1.

Effects of Cichorium Intybus L. Root Extract on Secretory Activity of the Stomach in Health and Ulcer Disease

Gastroprotective effect of Cichorium intybus L. root extract is demonstrated on H. Shay's model of experimental ulcer in rats. The effect is attributed to the antisecretory activity of the plant and stimulation of defense barrier function of the gastric mucosa. The regulatory effect of the phytocomplex on seasonal characteristics of the gastric secretory and defense functions in dogs with Basov's fistula is detected.

Motilin Stimulates Gastric Acid Secretion in Coordination with Ghrelin in Suncus murinus

Motilin and ghrelin constitute a peptide family, and these hormones are important for the regulation of gastrointestinal motility. In this study, we examined the effect of motilin and ghrelin on gastric acid secretion in anesthetized suncus (house musk shrew, Suncus murinus), a ghrelin- and motilin-producing mammal. We first established a gastric lumen-perfusion system in the suncus and confirmed that intravenous (i.v.) administration of histamine (1 mg/kg body weight) stimulated acid secretion. Motilin (0.1, 1.0, and 10 μg/kg BW) stimulated the acid output in a dose-dependent manner in suncus, whereas ghrelin (0.1, 1.0, and 10 μg/kg BW) alone did not induce acid output. Furthermore, in comparison with the vehicle administration, the co-administration of low-dose (1 μg/kg BW) motilin and ghrelin significantly stimulated gastric acid secretion, whereas either motilin (1 μg/kg BW) or ghrelin (1 μg/kg BW) alone did not significantly induce gastric acid secretion. This indicates an additive role of ghrelin in motilin-induced gastric acid secretion. We then investigated the pathways of motilin/motilin and ghrelin-stimulated acid secretion using receptor antagonists. Treatment with YM 022 (a CCK-B receptor antagonist) and atropine (a muscarinic acetylcholine receptor antagonist) had no effect on motilin or motilin-ghrelin co-administration-induced acid output. In contrast, famotidine (a histamine H2 receptor antagonist) completely inhibited motilin-stimulated acid secretion and co-administration of motilin and ghrelin induced gastric acid output. This is the first report demonstrating that motilin stimulates gastric secretion in mammals. Our results also suggest that motilin and co-administration of motilin and ghrelin stimulate gastric acid secretion via the histamine-mediated pathway in suncus.

Potent radioprotective effects of combined regimens of famotidine and vitamin C against radiation-induced micronuclei in mouse bone marrow erythrocytes

To investigate the radioprotective effect of the combination of famotidine and vitamin C against radiation-induced micronucleus formation in mouse bone marrow erythrocytes, various doses of famotidine or vitamin C or combinations thereof were administered intraperitoneally to adult male NMRI mice 2 h before 2 and 4 Gy γ-irradiation. The frequency of micronucleated polychromatic erythrocytes (MnPCEs) was scored in 5,000 polychromatic erythrocytes (PCEs), and the cell proliferation ratio [PCE/(PCE + NCE); NCE = normochromatic erythrocytes] was also calculated for each treatment group. Data were statistically evaluated using one-way ANOVA test. The results show that pretreatment with various doses of famotidine and vitamin C before γ-irradiation significantly reduced the frequency of MnPCEs with a protection factor (PF) of 2 and 1.7, respectively. Pretreatment with vitamin C also significantly increased the cell proliferation ratio, while famotidine had no effect. Combination of famotidine and vitamin C was more effective in reducing MnPCEs than each compound alone, leading to a PF of 4.3 after irradiation. Cell proliferation ratio was also significantly improved by the combination compared with the irradiated control groups. Both famotidine and vitamin C are potent scavengers of free radicals and reactive oxygen species, especially OH(·). The combination of the two compounds probably further enhances this activity, thus leading to high bone marrow protection.

Impact of Chronic Oral H2-Antagonist Therapy on Left Ventricular Systolic Function and Exercise Capacity

It has been suggested that H2-antagonists may adversely affect left ventricular systolic function. To assess the effects of cimetidine, famotidine, and ranitidine on exercise capacity and left ventricular systolic function, the authors conducted a randomized, double-blind, four-way crossover study in 15 healthy male volunteers with placebo control. Each subject underwent a maximal upright treadmill exercise test, aerobic metabolic assessment, and two-dimensional stress echocardiography on six separate occasions. The initial two treadmill exercise tests with aerobic metabolic assessment and stress echocardiography were performed to minimize the learning effect. In the final four evaluations, subjects were randomized to receive 7 days of oral treatment with cimetidine 400 mg twice daily, famotidine 40 mg daily, ranitidine 150 mg twice daily, and placebo. A comparison of exercise tests, aerobic metabolic assessment, and stress echocardiography results found no significant differences between any of the H2-antagonists and placebo. In addition, there were no significant differences in test results between cimetidine, famotidine, and ranitidine. Specifically, exercise treadmill time, maximal oxygen consumption, respiratory quotient, maximal exercise systolic and diastolic blood pressure, maximal exercise heart rate, left ventricular end-diastolic dimension, left ventricular end-systolic dimension, and ejection fraction were not different between treatments. The authors conclude that 7 days of oral treatment with cimetidine, famotidine, or ranitidine has no deleterious effect on exercise capacity or left ventricular systolic function in healthy subjects.

Famotidine suppresses osteogenic differentiation of tendon cells in vitro and pathological calcification of tendon in vivo

Heterotopic ossification or calcification follows any type of musculoskeletal trauma and is known to occur after arthroplasties of hip, knee, shoulder, or elbow; fractures; joint dislocations; or tendon ruptures. Histamine receptor H2 (Hrh2) has been shown to be effective for reducing pain and decreasing calcification in patients with calcifying tendinitis, which suggested that H2 blockers were effective for the treatment of tendon ossification or calcification. However, the detailed mechanisms of its action on tendon remain to be clarified. We investigated the mechanisms underlying H2 blocker-mediated suppression of tendon calcification, with a focus on the direct action of the drug on tendon cells. Famotidine treatment suppressed the mRNA expressions of Col10a1 and osteocalcin, ossification markers, in a tendon-derived cell line TT-D6, as well as a preosteoblastic one MC3T3-E1. Both of the cell lines expressed Hrh2; histamine treatment induced osteocalcin expression in these cells. Famotidine administration suppressed calcification in the Achilles tendon of ttw mice, a mouse model of ectopic ossification. These data suggest that famotidine inhibits osteogenic differentiation of tendon cells in vitro, and this inhibition may underlie the anti-calcification effects of the drug in vivo. This study points to the use of H2 blockers as a promising strategy for treating heterotopic ossification or calcification in tendon, and provides evidence in support of the clinical use of famotidine.

A new model of gastric bleeding induced in rats by aspirin plus clopidogrel under stimulation of acid secretion. Prophylactic effects of antiulcer drugs

We set up a new model of gastric bleeding induced by the luminal perfusion of aspirin (ASA) in rats pretreated with clopidogrel under conditions where acid secretion is stimulated, and examined the effect of antiulcer drugs on the bleeding. Under urethane anesthesia, acid secretion was stimulated by i.v. infusion of histamine (8 mg/kg/h), and two catheters were inserted into the stomach, one from the esophagus and another from the duodenum. The stomach was perfused with 25 mM ASA at a rate of 0.1 ml/min using an infusion pump, and gastric bleeding was measured as hemoglobin concentration in the perfusate collected every 15 min. Clopidogrel (30 mg/kg) was given orally 24 h before the perfusion. Various antiulcer drugs were given intraduodenally 30 min before the ASA treatment. Perfusion of the stomach with ASA provoked little gastric bleeding or damage even when acid secretion was stimulated. Pretreatment with clopidogrel significantly increased the bleeding and damage caused by ASA. The bleeding and lesions produced by ASA plus clopidogrel were significantly prevented by pretreatment with famotidine and omeprazole. Mucosal protective drugs such as rebamipide, irsogladine and teprenone also prevented gastric bleeding response to ASA/clopidogrel under conditions of acid secretion, although the effect was less pronounced than that of the antisecretory drugs. We conclude that clopidogrel increases gastric bleeding induced by ASA when acid secretion is stimulated. Both antisecretory and mucosal protective drugs are effective in reducing gastric bleeding under such conditions. This model is useful for the screening of drugs that protect against gastric bleeding.

Biochemical and histological investigation of famotidine effect on postischemic reperfusion injury in the rat ovary

BACKGROUND/PURPOSE

In this study, an investigation was performed on the ovarian tissue of rats subjected to ischemia-reperfusion for the effect of famotidine on certain parameters of oxidation-antioxidation, cell DNA damage, and histological appearance.

METHODS

The effects of famotidine on certain parameters of oxidation-antioxidation (total glutathione [tGSH], superoxide dismutase [SOD], malondialdehyde) and cellular DNA injury in the ovarian tissue of rats subjected to ischemia-reperfusion were investigated and underwent histological examination.

RESULTS

The results show levels of 5.2 ± 0.6 nmol/g protein for tGSH, 8.3 ± 0.8 U/g for SOD activity, and 7.7 ± 0.9 μmol/g protein for malondialdehyde (P < .0001 when compared with controls) in ovarian tissue subjected to ischemia-reperfusion following famotidine treatment. The tGSH levels in control rats and in a healthy animal group were, respectively, 1.76 ± 0.7 and 5.5 ± 0.3 nmol/g protein (P < .0001). The SOD activity was 3.2 ± 0.9 U/g in control and 9.2 ± 0.6 U/g in healthy animal tissues. The differences between the values in the treatment and the control group, and between the healthy animal group and the control group were both highly significant (P < .0001). It was also observed that famotidine prevented, to a significant extent, an increase in the level of 8-hydroxy-2-deoxyguanine/guanine, a DNA damage product, as compared with the control group.

CONCLUSION

These biochemical and histological results show that famotidine protects the ovarian tissue from ischemia-reperfusion injury.

Preparation and evaluation of famotidine polymorphs

The main objective of this study was to compare the behaviour of drug release among the famotidine polymorphs prepared by using various additives and solvents, by solvent evaporation method. The famotidine polyvinyl pyrrolidone polymorphs with different concentrations (0.5, 1 and 1.5%) were prepared by using solvent evaporation method. In these polymorphs of different concentrations 1% w/v polymorphs showed better release. Similarly, famotidine polymorphs of Tween 80 with different concentrations, polyethylene glycol 1% w/v and methanol was prepared. Famotidine polymorphs prepared the PVP (1% w/v) showed better drug release and solubility. DSC, FTIR, SEM and XRD studies were carried out. DSC studies revealed that PVP polymorphs were found to stable compared to other polymorphs. FTIR studies of the polymorphs prepared indicated that there was an interaction found in all polymorphs except PVP polymorphs indicating the absence of drug-additive interaction. SEM studies of PVP and methanol polymorphs revealed that they are tabular and prismatic and columnar respectively. These changes in morphology were due to variations in face dimensions and also properties of additives and solvent used in the preparation. XRD studies revealed that there is an increase in crystallinity in methanol polymorphs when compared to PVP polymorphs and pure drug. The mechanism of drug release was determined using zero order, first order and Hixon-Crowel equations. From the drug release kinetics these polymorphs followed first order and Hixon-Crowel release kinetics, exhibited fair linearity in their dissolution data. Further, in vivo studies were carried out for the evaluation of antiulcer activity. Based upon the drug release pattern and its kinetics only two of the prepared polymorphs of famotidine i.e. famotidine PVP polymorphs and famotidine methanol polymorphs were selected for animal studies. Antiulcer studies were carried out using pylorus ligation model and estimation of antioxidant parameters was also done. In these studies also polymorphs of PVP showed better antiulcer activity and also significant antioxidant activity when compared to famotidine (pure) and famotidine methanol polymorphs. Hence in the present investigation, amongst the various polymorphs of famotidine prepared, PVP polymorphs were found to possess good dissolution behaviour, stability and absence of drug additive interactions. Further, in vivo studies confirmed the better therapeutic action of these PVP polymorphs over the pure drug and famotidine methanol polymorphs.

Phosphodiesterase isozymes involved in regulating acid secretion in the isolated mouse stomach

The effect of subtype-selective phosphodiesterase (PDE) inhibitors on acid secretion was examined in mouse stomachs to investigate which PDE isozymes are involved in the local regulation of this secretion. Male DDY mice were used after 18 h fasting. An isolated stomach was incubated in an organ bath containing buffered solution gassed with 95% O(2)/5% CO(2), while the lumen was perfused with unbuffered solution gassed with 100% O(2). Acid secretion was measured at pH 5.4 using a pH-stat method. Histamine or pituitary adenylate cyclase activating polypeptide (PACAP) was added to the serosal solution. PDE inhibitors were added to the serosal solution 30 min before histamine or PACAP. The secretion of acid in the isolated stomach was increased by histamine or PACAP, and these responses were totally inhibited by famotidine. IBMX alone increased basal acid secretion and significantly enhanced the acid responses to histamine and PACAP. Among the PDE inhibitors tested, only rolipram (PDE4 inhibitor) significantly increased basal acid secretion and potentiated the acid responses to histamine and PACAP. The latter peptide increased histamine release into the medium, and this response was also enhanced by rolipram. Furthermore, rolipram significantly increased cAMP production induced in the isolated stomach by histamine and PACAP. These results suggest that PDE4 is involved in the local regulation of gastric acid secretion via the degradation of cAMP and that the PDE4 inhibitor rolipram increases the secretion of acid by potentiating acid production in parietal cells and enhancing histamine release from enterochromaffin-like cells.

Protective effect of mirtazapine on indomethacin-induced ulcer in rats and its relationship with oxidant and antioxidant parameters

Even though there are many drugs for the treatment of gastric ulcers, these drugs sometimes cannot succeed. Since the 1950s, antidepressant drugs have been used for several non-psychiatric indications. A lot of antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. This study aimed to investigate the antiulcer effects of mirtazapine and to determine its relationship with antioxidant mechanisms. The antiulcer activities of 15, 30, and 60 mg/kg mirtazapine have been investigated on indomethacin-induced ulcers in rats, and the results have been compared with that of the control group. Mirtazapine decreased the indomethacin-induced ulcers significantly at all doses used. Mirtazapine significantly increased the glutathione (GSH) level, which decreased in the control group given only indomethacin. All doses of mirtazapine significantly decreased the catalase (CAT) level in stomach tissue compared to the control. Additionally, all doses of mirtazapine reversed the decrease in the superoxide dismutase (SOD) level in the stomach tissue of control rats. And finally, all doses of mirtazapine decreased malondialdehyde (MDA) and myeloperoxidase (MPO) levels significantly compared to the control. In conclusion, the activation of enzymatic and non-enzymatic antioxidant mechanisms and the inhibition of some toxic oxidant mechanisms play a role in the antiulcer effect mechanism of mirtazapine. This new indication of mirtazapine will make it the first-choice drug in depressive patients with gastric ulcers.

[Efficiency of famotidin in prophylaxis of NSAIDs-induced gastropathy: result of multicenter research ZASLON-1 (protection of gastric mucosa from non-steroidal anti-inflammatory drugs]

This article presents results of the first Russian randomized study of NSAID-gastropaty prevention at patients receiving NSAIDS. Results of clinical and endoscopic monitoring of two groups of patients: 1st - 108 patients with AA or RA treated with diclofenac and famotidin and 2nd--116 patients with AA or RA receiving diclofenac treatment only. It was shown that combined use of diclofenac and famotidin reduces to 2.6 times frequency and significantly reduces severity of painful dyspepsia symptoms and antipain manifestations reduces more than twice frequency of erosive-ulcerous lesions of gastric mucosa and duodenum.

Effects of the histamine H2 receptor antagonist famotidine on the healing of colonic anastomosis in rats

BACKGROUND

Failure of anastomotic healing is one of the major complications in colorectal surgery. Because histamine plays an important role in immune and inflammatory reactions, we demonstrate the effects of famotidine on the healing of colonic anastomosis in rats.

METHODS

Twenty-eight Sprague-Dawley rats were used in the study. Excision and end-to-end anastomosis was performed in the distal colon of the rat. The Famotidine Group received 2 mg/kg/day famotidine; the Control Group received the same amount of saline. Bursting pressure of anastomoses and hydroxyproline content of perianastomotic tissues were evaluated on the third and seventh days following surgery.

RESULTS

Bursting pressures and hydroxyproline contents for the Famotidine Group were significantly lower than the equivalent parameters for the Control Group on both the third and seventh days post-surgery.

CONCLUSIONS

According to our findings, famotidine exerts detrimental effects on the anastomotic bursting pressure and hydroxyproline content of perianastomotic tissues in the colon of rats.

Comparison of the kinetic characteristics of inhibitory effects exerted by biguanides and H2-blockers on human and rat organic cation transporter-mediated transport: Insight into the development of drug candidates

In this study, the comparison of the transport of substrates (1-methyl-4-phenylpydinium (MPP) and tetraethyl ammonium (TEA)) and the inhibition potency of the inhibitors (biguanides and H(2)-blockers) for human and rat organic cation transporters (hOCTs and rOcts), and the inhibition type of inhibitors for these transporters were investigated using HEK293 cells that stably express hOCT/rOct. The concentration-dependent uptake of [(3)H]-MPP and [(14)C]-TEA by hOCT1-3/rOct1-3 had K(m) values similar to those in the literature. It was also deduced that MPP and TEA are competitive inhibitors for hOCT1-2/rOct1-2. The K(i) values for phenformin inhibition of [(3)H]-MPP and [(14)C]-TEA uptake by hOCT1-3/rOct1-3 were lower than that for metformin. The [(3)H]-MPP uptake by hOCT1/rOct1 and hOCT3/rOct3 was inhibited by famotidine and ranitidine whereas that by hOCT2/rOct2 was not. The inhibitory potency of cimetidine for hOCT1-2 was very weak. In most cases, the differences in the V(max)/K(m) values of substrates and the K(i) values of inhibitors between hOCT and rOct were minor. The acquisition of information on OCT/Oct mediated-transport and/or inhibition such as that presented in this report is very useful for further understanding of certain aspects of uptake, distribution, and excretion for drug candidates.

Antinociception induced by central administration of histamine in the formalin test in rats

In the present study, effects of intracerebroventricular (icv) administration of histamine, mepyramine (H1-receptor antagonist) and famotidine (H2-receptor antagonist) have been investigated on the formalin test in rats. Subcutaneous injection of formalin (50 microl, 1%) into the ventral surface of the left hind paw produced a marked biphasic pain response (first phase: 0-5 min and second phase: 15-45 min). All the performed treatments did not significantly influence the first phase of pain. Histamine at the doses of 10 and 40 microg and mepyramine and famotidine at the same doses of 20 and 80 microg, significantly (P < 0.05) decreased the late phase of formalin-induced pain. Pretreatments with mepyramine and famotidine at the same dose of 80 microg, significantly (P < 0.05) prevented the histamine (40 microg)-induced antinociception. These results indicate that brain histamine produces antinociception, and both central H1 and H2 receptors may involve in the histamine-induced antinociception in the formalin test in rats.

The effect of famotidine, esomeprazole, and ezetimibe on levothyroxine absorption

BACKGROUND

Recent literature describing the effect of gastric acid suppression on levothyroxine absorption has been inconsistent. Also, ezetimibe, a lipid-lowering compound that inhibits intestinal absorption of cholesterol, may interfere with levothyroxine absorption. The objective of this study was to measure changes in levothyroxine absorption before and after famotidine, esomeprazole or single-dose ezetimibe."

METHODS

We conducted levothyroxine absorption testing on 30 healthy volunteers, excluding those with thyroid disease. Subjects were randomized to receive one of three regimens: 1 week of either famotidine or esomeprazole, or a single dose of ezetimibe administered simultaneously with levothyroxine (n = 10 in each group). Baseline levothyroxine absorption testing was performed on all subjects using 600 mcg of Synthroid with thyroid hormone levels checked at 0, 2, 4, 6, and 8 hours after administration, and then repeated 6 weeks later, after administration of one of the three study drug regimens. The area under the curve (AUC) over 8 hours for serum thyroxine (T4), triiodothyronine (T3), and free T4 index, and the mean peak hormone levels achieved during levothyroxine absorption testing at baseline and following administration of one of the three study medications were compared using paired t-tests.

RESULTS

Peak mean hormone levels and AUCs of T4, T3, and free T4 index during absorption testing before and after each of three study medications did not differ. Results for differences before and after study medication did not reach significance even when using the subtractive correction method of AUC calculation.

CONCLUSIONS

No differences were noted in levothyroxine absorption after gastric acid suppression with 1 week of famotidine or esomeprazole. A simultaneously administered dose of ezetimibe did not significantly change levothyroxine absorption.

Effect of famotidine and lansoprazole on serum phosphorus levels in hemodialysis patients on calcium carbonate therapy

AIMS

Histamine H2 receptor antagonists (HRA) or proton pump inhibitors (PPI) are frequently administered to patients on hemodialysis, because their intestinal mucosa is fragile. Although three studies have indicated that concomitant HRA administration causes a decrease in the binding of phosphate by calcium carbonate, the HRA doses tested in these studies were 2-4 times higher than the recommended dose for hemodialysis patients. In addition, it remains unclear whether PPI therapy affects serum phosphate levels in hemodialysis patients taking calcium carbonate. Accordingly, the aim of this study was to evaluate the influence of lansoprazole and the recommended dose of famotidine on serum phosphate and calcium levels in hemodialysis patients.

METHODS

The study included 115 hemodialysis patients who were taking calcium carbonate and who were also treated with either famotidine (10 mg/day) or lansoprazole (30 mg/day). Changes of the mean serum phosphate and calcium levels over 2 months before and after the start of famotidine or lansoprazole therapy were compared. The same parameters were also compared when famotidine was switched to lansoprazole.

RESULTS

The mean serum phosphate level increased significantly after administration of either famotidine or lansoprazole (by 6.6 +/- 21.9% or 13.0 +/- 26.3%, p = 0.032 and p = 0.029, respectively). The mean serum calcium level was unchanged after administration of famotidine, but showed a significant decrease after administration of lansoprazole (by 3.44 +/- 7.73%, p = 0.013). Therefore, the calcium x phosphorus product was significantly increased by administration of famotidine, but not by administration of lansoprazole (6.68 +/- 23.37% and 8.73 +/- 27.41%, p = 0.046 and p = 0.251, respectively). When famotidine was switched to lansoprazole, the serum phosophate level did not change, but serum calcium decreased significantly by 3.8 +/- 13.0% (p = 0.0006).

CONCLUSION

Not only administration of 20 mg/ day of famotidine as previously reported, but also 10 mg/day of this drug (the recommended dose for hemodialysis patients) caused a significant increase of serum phosphate in patients taking calcium carbonate. PPIs have been reported to show no effect on the serum phosphate level, but 30 mg/day of lansoprazole also caused a significant increase of serum phosphate in patients taking calcium carbonate.

Gastroprotective and antioxidant effects of montelukast on indomethacin-induced gastric ulcer in rats

Montelukast, a selective reversible cysteinyl leukotriene D(4)-receptor (LTD(4) receptor) antagonist, is used in the treatment of asthma. We have investigated alterations in the glutathione (GSH) and activity levels of antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione reductase (GR)] and myeloperoxidase (MPO), as markers of the ulceration process following oral administration of montelukast, lansoprazole, famotidine, and ranitidine, respectively, in rats with indomethacin-induced ulcers. In the present study, we found that 1) montelukast, lansoprazole, famotidine, and ranitidine all reduced the development of indomethacin-induced gastric damage, with this reduction occurring at a greater magnitude for montelukast, famotidine, and lansoprazole than for ranitidine; 2) montelukast and ranitidine both alleviated increases in the activity levels of CAT and GST enzymes resulting from gastric injury; 3) montelukast and ranitidine both ameliorated depressions in the GSH and activity levels of SOD and GR enzymes caused by indomethacin administration; and 4) all doses of montelukast, lansoprazole, and ranitidine decreased amplification of MPO activity resulting from induced gastric injuries. These results suggest that the gastroprotective effects of montelukast on indomethacin-induced ulcerations can be attributed to its ameliorating effect on oxidative damage and MPO activity.

Modulation of gamma-ray-induced apoptosis in human peripheral blood leukocytes by famotidine and vitamin C

To study the radioprotective effects of vitamin C and famotidine against radiation-induced apoptosis in human peripheral blood leukocytes, peripheral blood was obtained from six healthy volunteers including three males and three females. Twelve microlitres of blood sample diluted in 1 ml complete RPMI-1640 medium was irradiated with various doses of gamma-rays (4, 8 and 12 Gy) in the presence or absence of various doses of vitamin C and famotidine. After 48 and 72 h incubation in a 37 degrees C CO(2) incubator, neutral comet assay was performed for all samples. At least 1000 cells were analyzed for each sample for presence of apoptosis. Data were statistically evaluated using Mann-Whitney non-parametric and ANOVA tests. Results show a significant increase in apoptosis induction following gamma-irradiation with a dose dependent manner compared to controls (p<0.001). Presence of famotidine at 200 microg/ml produced a significant protective effect against radiation-induced apoptosis for various doses of radiation. Similar effects were observed for vitamin C at much lower doses (10 microg/ml). Dose reduction factor (DRF) calculated for famotidine treatment was about 1.5, and above 2 for vitamin C treatment. These results suggest that both vitamin C and famotidine suppresses radiation-induced apoptosis when used with various doses of gamma-irradiation (4-12 Gy) probably via *OH radical scavenging and an intracellular antioxidation mechanism.

Differential effects of histamine on Leydig cell and testicular macrophage activities in wall lizards: precise role of H1/H2 receptor subtypes

The present study in the wall lizard, Hemidactylus flaviviridis, was aimed to understand the role of histamine (HA) in the regulation of Leydig cell and testicular macrophage activities, for the first time, in ectothermic vertebrates. Although HA did not affect the testosterone production from unstimulated Leydig cells, it had dual concentration-related effects, stimulatory at a low concentration of 10(-10) M while inhibitory at a high concentration of 10(-5) M, on FSH-induced testosterone production. This suggests that HA did not influence the basal Leydig cell steroidogenesis, but modulated the FSH-stimulated testosterone production in a biphasic manner depending upon its concentration. However, HA failed to affect the FSH-stimulated Leydig cell proliferation, indicating that HA modulated the testosterone production from Leydig cells without influencing their proliferation in wall lizards. HA, apart from Leydig cells, differentially regulated the testicular macrophage immune responses. It inhibited phagocytosis and superoxide production at high concentration (10(-5) M), while stimulated superoxide production and could not affect phagocytosis at low concentration (10(-10) M). Using selective H1 and H2 antagonists, pyrilamine and famotidine respectively, H1 receptor subtype was seen responsible for mediating the inhibitory effect of HA on Leydig cell steroidogenesis and testicular macrophage immune responses at high concentration, while H2 receptors were involved for the stimulation at low concentration.

In vitro availability studies of enoxacin in presence of H2 receptor antagonists

Enoxacin is a second-generation quinolone with increased antibacterial activity both in potency as well as in terms of broad spectrum against a wide range of clinically important pathogens over the first generation quinolones and produces its effect by inhibiting bacterial enzyme DNA gyrase. There are a number of drug interactions reported for enoxacin. On the other hand H2-receptor antagonists block gastric acid secretion and some cardiovascular effects of histamine. As the later drugs are used for a long-term therapy, they may be coadministered with other drugs. In present study in vitro release of enoxacin in presence of cimetidine, ranitidine and famotidine has been studied on a B.P. 2003 dissolution test apparatus and compared with the availability of enoxacin and H2-receptor antagonists alone. The interacting drugs were analyzed spectrophotometrically. These studies were carried out in simulated gastric juice, simulating empty stomach, simulated intestinal juice (pH 9) and buffers of pH 7.4 simulating blood pH at 37 degrees C. In order to support these interaction studies, the effect of H2-receptor antagonists on the antibacterial efficacy (MIC) of enoxacin was also studied by turbidity method and compared with parent drug against Staphylococcus aureus, Streptococcus pyogens, Streptococcus pneumoniae, Enterococcus, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis and Bacillus subtilis. On the basis of these results, it is suggested that enoxacin should be coadministered with care along with H2-receptor antagonists especially in case of ranitidine, although chances of adverse reactions are rare but decrease in MIC of enoxacin may result in delayed effect or require prolonged use of the drug.

Histamine stimulation of MMP-1(collagenase-1) secretion and gene expression in gastric epithelial cells: role of EGFR transactivation and the MAP kinase pathway

BACKGROUND AND AIMS

GPCR stimulation by various ligands including histamine has been shown to transactivate the epidermal growth factor receptor (EGFR). This study examines the functional interactions between the H2 receptor and the EGFR in the regulation of matrix metalloproteinase-1 (MMP-1) secretion and gene expressions in cultured gastric epithelial cells.

METHODS

AGS cells were incubated for up to 24 h with either histamine or heparin binding-epidermal growth factor (HB-EGF) and MMP-1 release was determined by immunoassay. MMP-1 responses to histamine and HB-EGF were further tested by the use of H2 receptor antagonist, EGFR inhibitor and mitogen activator protein kinase (MAPK) inhibitor. The role of EGFR in MMP-1 release was further tested in cells transfected with specific EGFR siRNA. EGFR and ERK1/2 phosphorylation was determined by Western blot analysis. MMP-1 gene expression was determined by RNase protection assay (RPA).

RESULTS

Histamine and HB-EGF caused a dose-dependent release of MMP-1 with maximal responses that were 2.7- and 4.5-fold greater, respectively, than control, P<0.001. Famotidine prevented histamine-mediated MMP-1 release and AG1478 and EGFR siRNA completely inhibited MMP-1 secretion stimulated by both histamine and HB-EGF. Both histamine and HB-EGF stimulation of MMP-1 release was associated with activation of ERK1/2. MAPK inhibition also prevented histamine-and HB-EGF-induced MMP-1 secretion. Results of MMP-1 gene expression, either stimulatory or inhibitory, paralleled responses to MMP-1 secretion.

CONCLUSION

Histamine stimulation of the H2 receptor on AGS cells evoked MMP-1 secretion and gene up regulation that was dependent on transactivation of the EGFR and downstream activation of MAPK.

Antiulcer and in vitro antioxidant activities of Jasminum grandiflorum L

The study was aimed at evaluating the antiulcer and antioxidant activities of 70% ethanolic axtract of leaves of Jasminum grandiflorum L. (JGLE). The leaves of Jasminum grandiflorum L. (Family: Oleaceae) is used in folk medicine for treating ulcerative stomatitis, skin diseases, ulcers, wounds, corns - a hard or soft hyperkeratosis of the sole of the human foot secondary to friction and pressure (Stedman's Medical Dictionary, 28th ed. Lippincott Williams & Wilkins, Philadelphia. p. 443), etc., Antiulcerogenic activity of JGLE (100 and 200 mg/kg, b.w., orally) was evaluated employing aspirin + pylorus ligation (APL) and alcohol (AL) induced acute gastric ulcer models and ulcer-healing activity using acetic acid-induced (AC) chronic ulcer model in rats. Both the antisecretory and cytoprotection hypothesis were evaluated. The antioxidant activity of JGLE has been assayed by using in vitro methods like 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH) assay, reductive ability, superoxide anion scavenging activity, nitric oxide scavenging activity and total phenolic content, in order to explain the role of antioxidant principles in the antiulcerogenic activity of the extract. There was a significant (P<0.01) dose-dependent decrease in the ulcerative lesion index produced by all the three models in rats as compared to the standard drug famotidine (20 mg/kg, b.w. orally). The reduction in gastric fluid volume, total acidity and an increase in the pH of the gastric fluid in APL rats proved the antisecretory activity of JGLE. Additionally, JGLE completely healed the ulcer within 20 days of treatment in AC model as evidenced by histopathological studies. Like antiulcer activity, the free radical scavenging activities of JGLE depends on concentration and increased with increasing amount of the extract. These results suggest that leaves of Jasminum grandiflorum possess potential antiulcer activity, which may be attributed to its antioxidant mechanism of action.

Study on the antinociceptive action of Tyr-K-MIF-1, a peptide from the MIF family

1. Tyr-K-MIF-1 is a melanocyte inhibiting factor (MIF) neuropeptide, isolated from the brain. Opposite to other MIFs (Tyr-MIF-1, Tyr-W-MIF-1), it has a very low affinity for opiate mu-receptors, but interacts with Tyr-MIF-1 specific binding sites. Tyr-MIF-1 and Tyr-W-MIF-1 evoke antinociception mainly by activating opioid receptors. We investigated the possible antinociceptive effect of Tyr-K-MIF-1 and the involvement of histaminergic system in its mechanism of action. 2. Tested on rats by paw-pressure test, Tyr-K-MIF-1 (0.5, 1 and 2 mg kg(-1)) was associated with short-lasting analgesia, which was abolished by naloxone (1 mg kg(-1)). 3. Injected intraperitoneally (i.p.) 15 min before Tyr-K-MIF-1, antagonists of H(1) (diphenhydramine, 100 mg kg(-1)) or H(2) (famotidine, 0.3 and 0.6 mg kg(-1)) histamine receptors diminished peptide antinociceptive effect. Simultaneous H(1)- and H(2) blockade, as well as pretreatment with 5 mg kg(-1) dimaprit (H(2) agonist) abolished Tyr-K-MIF-1-induced analgesia. Tyr-K-MIF-1-induced analgesia was also abolished by treatment with R-(alpha)-methylhistamine (10 mg kg(-1), i.p.), an H(3) histamine receptor agonist that acts to inhibit histamine release. 4. Our results together with data reported in the literature support the conclusion that activation of the histaminergic system is involved in the mechanism of Tyr-K-MIF-1-induced antinociception.

In vivo gamma-rays induced initial DNA damage and the effect of famotidine in mouse leukocytes as assayed by the alkaline comet assay

Ionizing radiation induces a variety of lesions in DNA, each of which can be used as a bio-indicator for biological dosimetry or the study of the radioprotective effects of substances. To assess gamma ray-induced DNA damage in vivo in mouse leukocytes at various doses and the effect of famotidine, blood was collected from Balb/c male mice after irradiation with 4 Gy gamma-rays at different time intervals post-irradiation. To assess the response, mice were irradiated with doses of gamma-rays at 1 to 4 Grays. Famotidine was injected intra-peritoneally (i.p) at a dose of 5 mg/kg at various time intervals before irradiation. Four slides were prepared from each sample and alkaline comet assay was performed using standard protocols. Results obtained show that radiation significantly increases DNA damage in leukocytes in a dose dependent manner (p < 0.01) when using appropriate sampling time after irradiation, because increasing sampling time after irradiation resulted in a time dependent disappearance of DNA damage. Treatment with only 5 mg/kg famotidine before 4 Gy irradiation led to almost 50% reduction in DNA damage when compared with those animals which received radiation alone. The radioprotective capability of famotidine might be attributed to radical scavenging properties and an anti-oxidation mechanism.

Inhibition of neutrophil activation by lafutidine, an H2-receptor antagonist, through enhancement of sensory neuron activation contributes to the reduction of stress-induced gastric mucosal injury in rats

Sensory neuron activation reduces water-immersion restraint stress (WIR)-induced gastric mucosal injury by inhibiting neutrophil activation through increase in endothelial production of prostacyclin. This study was designed to examine whether lafutidine, which is an H(2)-receptor antagonist and activates sensory neurons, inhibits neutrophil activation, thereby reducing WIR-induced gastric mucosal injury. Lafutidine enhanced WIR-induced increases in gastric tissue levels of calcitonin gene-related peptide (CGRP) and 6-keto-PGF(1alpha), a stable metabolite of prostacyclin, whereas famotidine, another H(2)-receptor antagonist, did not. Such lafutidine-induced increases in gastric tissue levels of 6-keto-PGF(1alpha) were reversed by pretreatment with capsazepine, an inhibitor of sensory neuron activation, CGRP(8-37), a CGRP antagonist, and indomethacin. Lafutidine inhibited acid-induced exacerbation of gastric mucosal injury in animals subjected to WIR by inhibiting neutrophil activation, whereas famotidine did not. Lafutidine synergistically increased CGRP release from isolated rat dorsal root ganglion neurons in the presence of anandamide, but famotidine did not. These observations suggest that lafutidine might reduce WIR-induced gastric mucosal injury not only by inhibiting acid secretion but also by inhibiting neutrophil activation through enhancement of sensory neuron activation.

Promotion of cutaneous wound healing by famotidine in Wistar rats

BACKGROUND & OBJECTIVE

Drugs like famotidine, omeprazole and sucralfate which have been reported to promote the healing of gastric ulcers, may have the same effect on cutaneous wounds. Due to paucity of information in this regard, the present study was planned to investigate the effect of these drugs on resutured incision, excision and dead space wounds in Wistar rats.

METHODS

Resutured incision, excision and dead space wounds were inflicted under light ether anaesthesia aseptically. Control animals received vehicle and other groups received famotidine, omeprazole and sucralfate orally for a period of 10 days in the incision and dead space wounds, whereas in excision wounds till complete closure. On the 11th day after estimating breaking strength of the resutured incision wounds, animals were sacrificed and granulation tissue removed from dead space wounds to estimate the breaking strength and hydroxyproline content. Quantification of granulation tissue and histological studies were also carried out. Wound closure rate, epithelization time and scar features were studied in the excision wound models from the day of famotidine till complete closure of the wound.

RESULTS

Only famotidine significantly promoted the healing process in all the three wound models studied. Histopathological studies revealed increased collagen content and granulation tissue in famotidine treated group compared to control.

INTERPRETATION & CONCLUSION

In all the three wound models studied famotidine promoted wound healing whereas omeprazole and sucralfate did not do so. The pro healing effect of famotidine needs to be explored clinically.

Pharmacokinetic and Pharmacodynamic Properties of Lafutidine after Postprandial Oral Administration in Healthy Subjects: Comparison with Famotidine

Lafutidine, a histamine H(2)-receptor antagonist, inhibits gastric acid secretion during the daytime, however, the relationship between the plasma concentration and the drug response remains unclear. The aim of this study was to compare the pharmacokinetic and pharmacodynamic properties of lafutidine and famotidine following postprandial oral administration. After a lafutidine tablet (10 mg), famotidine tablet (20 mg), or water only (control) was administered, blood samples were taken and intragastric pH was measured. The plasma concentrations of lafutidine and famotidine were determined by HPLC, and the median intragastric pH values per 30 min were used as the degrees of gastric acid suppression. Data were analyzed based on a one-compartment pharmacokinetic model and a sigmoid E(max) pharmacodynamic model. Lafutidine plasma concentrations rapidly increased after administration; famotidine required some time to increase the plasma concentrations, requiring an absorption lag time in the pharmacokinetic model. Between the plasma concentration and DeltapH (the difference in intragastric pH by the drug vs. control), lafutidine showed an anticlockwise hysteresis loop which indicated equilibration delay between the plasma concentration and effect site, requiring an effect site compartment in the pharmacodynamic model; famotidine showed more parallel relationship. These results indicated that the pharmacokinetic and pharmacodynamic properties of lafutidine after postprandial oral administration were different from those of famotidine at least 4.5 h after dosing.

Effects of histamine 2 receptor antagonists on endothelial-neutrophil adhesion and surface expression of endothelial adhesion molecules induced by high glucose levels

Neutrophil-endothelial adhesion is a crucial step in vascular inflammation and is recognized as a direct cause of serious atherosclerosis-mediated diseases. We previously demonstrated that high concentrations of glucose increased adhesion in a protein kinase C (PKC)-dependent manner within 48 h of administration by increasing the surface expression of endothelial adhesion molecules. In this study, we focused on the effects of histamine 2 receptor antagonists on endothelial-neutrophil adhesion and on the surface expression of endothelial adhesion molecules mediated by high glucose levels. Histamine 2 receptor antagonists have pleiotropic effects; they not only block the secretion of gastric acid, but also inhibit cell-cell adhesion, resulting in inhibition of metastasis. However, relevant mechanisms of action are not yet fully understood. Of three histamine 2 receptor antagonists (cimetidine, ranitidine, and famotidine), only cimetidine significantly attenuated adhesion mediated by 48-h incubation with 27.8 mM glucose. Cimetidine was found to decrease the surface expression of endothelial adhesion molecules intercellular adhesion molecule-1 and P-selectin, but not E-selectin. To determine the effects of cimetidine on intracellular level, we examined the effects of cimetidine on PKC-induced changes in adhesion, as well as the effects of nitric oxide (NO) synthase inhibitors on cimetidine. We found that NO synthase inhibitors reduced the inhibitory effects of cimetidine, whereas cimetidine did not affect adhesion mediated by a PKC activator. These data suggest that cimetidine acts directly on endothelial cells to inhibit high-glucose-induced expression of adhesion molecules and neutrophil adhesion mediated by increasing endothelial NO production, but not by inhibiting PKC.

The Quantitative Prediction of Bitterness-Suppressing Effect of Sweeteners on the Bitterness of Famotidine by Sweetness-Responsive Sensor

The purpose of the present study was the quantitative prediction of the bitterness-suppressing effect of sweeteners (sucrose or sugar alcohols) on the bitterness of famotidine (or quinine sulfate as control) solutions using an artificial taste sensor. Firstly, we examined the response characteristics of the sensor response to sweetness. The sensor membrane is charged negatively in the presence of sweeteners, which tend to receive protons from one of the components of the sensor membrane. The magnitude of the sensor response was shown to increase in direct proportion to the concentration of the sweetener. Secondly, we used direct or indirect methods to evaluate and predict the bitterness-suppressing effect of sweeteners on 1 mg/ml famotidine and 81.4 microM quinine sulfate solutions. In direct method, a regression between the sensor output of the sweetness-responsive sensor and the bitterness intensity obtained in human gustatory tests of famotidine solutions containing sweeteners at various concentrations, was performed. As a result, we were able to predict directly the bitterness intensity of the mixed solution. Finally, we also evaluated the bitterness intensity of the dissolution media of commercially available, orally disintegrating tablets containing famotidine by the combined usage of bitterness- and sweetness-responsive sensor. We found that the sugar alcohols in the tablet seem to be effective in the bitterness-suppression of famotidine from these tablets, especially in the initial phase (within 30 s) of the disintegration process.

Effects of rabeprazole or famotidine during cardiac surgery on perioperative gastric and esophageal pH readings

OBJECTIVES

Upper gastrointestinal bleeding, particularly from a stress-induced duodenal ulcer, is an extremely important perioperative complication in cardiovascular surgery.

METHODS

In the present study, 33 patients undergoing elective open heart surgery between July 2000 and February 2001 were allocated to either a famotidine (FAM) or rabeprazole (RPZ) group to examine the perioperative gastric and esophageal pH readings, in conjunction with an investigation into the effect of infection with Helicobacter pylori (HP).

RESULTS

Postoperative upper gastrointestinal bleeding did not occur in either group, and the intraoperative and postoperative mean gastric pH readings, as well as the holding time pH>6, suggested sufficient acid suppression by either drug. Gastric acid secretion was less strongly suppressed in HP-negative patients in the FAM group, but was unaffected by HP infection status in the RPZ group.

CONCLUSION

The FAM group and RPZ group revealed a sufficient effect of gastric acid suppression. It was indicated that FAM had an insufficient effect of gastric acid suppression for HP-negative patients.

Expression of HSP72 in the gastric mucosa is regulated by gastric acid in rats-correlation of HSP72 expression with mucosal protection

BACKGROUND AND AIM

The real mechanism of adaptive cytoprotection in the gastric mucosa is not well established. In the present study, we investigated the effect of acid suppressing agents on a 72-kDa heat shock protein (HSP72) expression, which is known as endogenous cytoprotective factor, in the gastric mucosa. Also, the association of gastric mucosal protective function against HCl-challenge was compared between HSP72-induced and -reduced group.

MATERIALS AND METHODS

Expression of HSP72 was measured by Western blotting in the gastric mucosa before and after administration of famotidine or omeprazole. The gastric mucosal protective function against 0.6 N HCl was compared between control group and HSP72-reduced group. Also, the effect of increased expression of gastric HSP72 by additional administration of zinc sulfate or zinc L-carnosine, which is known as HSP72-inducer, on mucosal protective function was studied.

RESULTS

HSP72 expression in the gastric mucosa was reduced by acid suppressing agents. The lowest expression level of HSP72 was observed 12 h (famotidine, H2-receptor antagonist) or 48 h (omeprazole, proton pump inhibitor) after administration. The gastric mucosal protective ability against 0.6 N HCl was also reduced when HSP72 expression was decreased by famotidine or omeprazole. This phenomenon was reversed by HSP72 induction by additional administration of zinc derivatives.

CONCLUSION

Our results might indicate that the expression of HSP72 in the gastric mucosa is physiologically regulated by gastric acid, and that HSP72 induction could be important in view of mucosal protection especially when HSP72 expression is reduced by administration of acid suppressing agents such as proton pump inhibitor or H2 receptor antagonist.

Histamine mediates the stimulatory action of ghrelin on acid secretion in rat stomach

Ghrelin, a novel growth hormone-releasing peptide, is present in the rat and human stomach and is known to stimulate acid secretion and stomach motility. However, the mechanism of action of ghrelin is not fully understood. In the present study, we attempted to elucidate the role of histamine in ghrelin-induced acid secretion in rat stomach. Intravenous administration of ghrelin at 0.8 to 20 microg/kg dose dependently increased gastric acid secretion, as measured by the gastric lumen perfusion method. The maximum response was almost equal to that of gastrin (20 microg/kg). These actions were abolished by bilateral subdiaphragmatic vagotomy. Famotidine (0.33 mg/kg) also completely inhibited the effects of ghrelin. Furthermore, ghrelin increased histidine decarboxylase (HDC) messenger RNA (mRNA) levels, as measured by real-time reverse transcription-polymerase chain reaction using LightCycler. The action of ghrelin on HDC mRNA was abolished by vagotomy. Ghrelin did not affect histamine release from isolated vascularly perfused rat stomach. Taken together, these results suggest that ghrelin stimulates gastric acid secretion via a mechanism involving activation of vagal efferent nerve and histamine release from gastric enterochromaffin-like cells.

Formulation of Solid Dosage Forms to Overcome Gastric pH Interaction of the Factor Xa Inhibitor, BMS-561389

PURPOSE

The purpose of the study was to investigate the specific mechanism by which elevated gastric pH reduces the absorption of BMS-561389, a factor Xa inhibitor, and to develop a solid formulation strategy to overcome this gastric pH interaction.

METHODS

A dissolution method in an acetate buffer at pH 5.5 was used to evaluate the dissolution behavior of the tablet formulation. A precipitation model was used to screen different excipients for their potential to minimize the pH-dependent absorption of BMS-561389. Excipients that showed promise in the precipitation model were incorporated in modified tablet formulations. Dissolution rate of the modified tablets was also determined by the acetate buffer method. A canine model for pH-dependent absorption was subsequently used to evaluate the tablet formulations.

RESULTS

Dissolution studies suggested that the reduced absorption of the original formulation was the result of the precipitation of the poorly water-soluble free base during the initial dissolution of the salt. Modified tablets containing organic acids, sulfobutylether-beta-cyclodextrin, or povidone showed enhanced dissolution as compared with the original formulation. Drug absorption from the tablet containing tartaric acid was substantially independent of gastric pH in the canine model.

CONCLUSION

A multitier approach was successful in identifying a solid dosage form that minimizes the pH-dependent absorption of this drug candidate.

Blockade of histamine H2 receptors protects the heart against ischemia and reperfusion injury in dogs

We have previously reported that histamine H(2) blockers may be cardioprotective in patients with chronic heart failure. Since both endogenous histamine and histamine H(2) receptors are present in heart tissue, we tested the hypothesis that the blockade of histamine H(2) receptors mediates protection against reversible or irreversible ischemia and reperfusion injury. In open-chest dogs, the left anterior descending coronary artery was occluded for 90 minutes, followed by reperfusion for 6 hours. Administration of famotidine and cimetidine from 10 minutes before occlusion until after 1 hour of reperfusion reduced infarct size (17.0 +/- 4.1% and 17.8 +/- 2.9% vs. 36.9 +/- 5.9% of the solvent group, respectively) Famotidine administration only during the reperfusion period for 1 hour also attenuated infarct size (22.5 +/- 3.5%). There were no differences in either area at risk or collateral flow among the groups. In another set of experiments, we decreased coronary perfusion pressure in dogs so that the coronary blood flow decreased to 50% of the non-ischemic level. In such conditions, we observed the increases in histamine release compared with non-ischemic conditions (0.04 +/- 0.03 to 0.28 +/- 0.13 ng/ml, p < 0.05). Famotidine improved anaerobic myocardial metabolism gauged by both lactate extraction ratio and myocardial oxygen consumption. We conclude that the blockade of histamine H(2) receptors mediates improvements in the anaerobic myocardial metabolism, and thus protects against ischemia and reperfusion injury.

Histamine increases sickle erythrocyte adherence to endothelium

Complications of sickle cell anaemia include vascular occlusion triggered by the adherence of sickle erythrocytes to endothelium in the postcapillary venules. Adherence can be promoted by inflammatory mediators that induce endothelial cell adhesion molecule expression and arrest flowing erythrocytes. The present study characterised the effect of histamine stimulation on the kinetics of sickle cell adherence to large vessel and microvascular endothelium under physiological flow. Increased sickle cell adherence was observed within minutes of endothelial activation by histamine and reached a maximum value within 30 min. At steady state, sickle cell adherence to histamine-stimulated endothelium was 47 +/- 4 adherent cells/mm(2), 2.6-fold higher than sickle cell adherence to unstimulated endothelial cells. Histamine-induced sickle cell adherence occurred rapidly and transiently. Studies using histamine receptor agonists and antagonists suggest that histamine-induced sickle cell adhesion depends on simultaneous stimulation of the H(2) and H(4) histamine receptors and endothelial P-selectin expression. These data show that histamine release may promote sickle cell adherence and vaso-occlusion. In vivo histamine release should be studied to determine its role in sickle complications and whether blocking of specific histamine receptors may prevent clinical complications or adverse effects from histamine release stimulated by opiate analgesic treatment.

Effects of diphenhydramine and famotidine on lipid peroxidation and activities of antioxidant enzymes in different rat tissues

The potential antioxidant activity of diphenhydramine (histamine H1-receptor antagonist) and famotidine (histamine H2 receptor antagonist) was studied. Diphenhydramine inhibited the spontaneous, Fe(II)-induced and Fe(II)/ascorbate-induced lipid peroxidation, while famotidine showed a biphasic concentration-dependent effect on spontaneous lipid peroxidation (a stimulation by 1 mM and an inhibition by 5 mM) and increased Fe(II)-induced- and inhibited Fe(II)/ascorbate-induced lipid peroxidation in the rat liver and brain. Both drugs decreased *OH-provoked deoxyribose degradation in Fenton-type systems and inhibited O2- -provoked reduction of nitro-blue tetrazolium and ferrycytochrome C, but famotidine effect was stronger than that of diphenhydramine. The significant famotidine-induced inhibition of nitro-blue tetrazolium reduction might be underlain by the stimulation of superoxide dismutase activity. Famotidine and diphenhydramine did not alter the catalase activity in all tissue preparations, except for its concentration of 5 mM (a complete inhibition). The present results suggest a beneficial effect of histamine H1 and H2-blockers, especially famotidine, as antioxidants and/or metal chelators, which might be an additional explanation of their therapeutic action.

Mast cell activation and degranulation occur early during induction of periosteal bone resorption

We have previously postulated that mast cells participate in the cellular network involved in osteoclastic resorption, probably through histamine release. In this study, we examined mast cell activation and histamine release during origination of resorption. Groups of 10 rats were killed 0, 0.5, 1, 1.5, 3, 6, 9, 12 and 18 h after induction of resorption in a synchronized model of cortical resorption along the mandible. The total number of mast cells was transiently decreased by about one-third at 1 and 9 h. Mast cell activation was monitored by Alcian blue-safranin staining. Early after induction, mast cells started to release their mediator stores; complete release led to the apparent disappearance of the cells with the staining technique used. Histamine immunostaining confirmed the release of histamine and its diffusion in the extracellular environment. Massive degranulation was observed at 1.5 and 9 h with toluidine blue staining. Cell recovery, assessed in terms of histidine decarboxylase expression, occurred gradually. The number of ED1+ osteoclast precursors strongly increased from 12 h up to 18 h. Most parameters had returned to baseline at 18 h, except the ED1+ cells. H2 receptor inhibition with famotidine strongly decreased ED1+ osteoclast precursors at 12 h and subsequently osteoclasts at the peak of resorption. These data support a role of mast cells in resorption origination. They show an early and transient intervention of mast cells in the events regulating the recruitment of circulating osteoclast precursors and ultimately of resorption. Mast cell activation and degranulation induce the release of mediators, particularly histamine acting through its H2 receptors, which are likely involved in these reactions.

Lafutidine, a newly developed antiulcer drug, elevates postprandial intragastric pH and increases plasma calcitonin gene-related peptide and somatostatin concentrations in humans: comparisons with famotidine

Lafutidine, a newly developed histamine H(2)-receptor antagonist, inhibits daytime (i.e., postprandial) as well as nighttime gastric acid secretion in clinical studies. It also has gastroprotective activity that particularly affects mucosal blood flow in rats. This study focused on the efficacy of lafutidine on plasma concentrations of gastrointestinal peptides in humans. Six healthy male volunteers aged 23-32 years without Helicobacter pylori infection were orally administered either 10 mg lafutidine, 20 mg famotidine, or water only (control) 30 min after a standard meal (650 kcal). Plasma concentrations of lafutidine and famotidine were highest from 90 to 150 min after administration. Intragastric pH was elevated after both lafutidine and famotidine compared with the control. Plasma concentrations of calcitonin gene-related peptide (CGRP) and somatostatin were significantly increased after lafutidine at 60 and 90 min. We concluded that lafutidine increases plasma concentrations of CGRP and somatostatin in humans, which may result in inhibition of postprandial acid secretion and gastroprotective activity.

Influence of famotidine on verapamil pharmacokinetics in rats

The effect of famotidine (4 mg/kg, p.o.) on the kinetic profile of co-administered verapamil (20 mg/kg(-1), p.o.) was studied in the rat. Plasma verapamil levels were collected serially for 12 h and measured using sensitive HPLC method. The pharmacokinetic parameters (elimination half-life, area under the plasma concentration-time curve, peak plasma levels and the times to attain these plasma levels) of verapamil were evaluated in the rat. The results indicate that co-administered famotidine did not significantly alter the pharmacokinetic profile of verapamil in the rat. The present finding suggests that famotidine may safely be co-administered with verapamil but clearly further studies in human subjects are needed to reliably rule out the potential interaction of these two drugs.

Alteration of intracellular histamine H2 receptor cycling precedes antagonist-induced upregulation

Long-term administration of a histamine H2 receptor (H2R) antagonist (inverse agonist) induces upregulation of H2R in parietal cells, which may be relevant to the rebound hypersecretion of gastric acid that occurs after withdrawal of treatment. The mechanisms underlying this effect are unknown. We hypothesized that the H2R upregulation could be related to receptor trafficking and used H2R-green fluorescent protein (H2R-GFP) to test the hypothesis. Human H2R-GFP was generated and functionally expressed in HEK-293 cells. Binding of the H2R antagonist [3H]tiotidine was performed to quantify H2R expression, and H2R-GFP was imaged in living cells by confocal and evanescent wave microscopy. The binding affinity of [3H]tiotidine was not significantly different between H2R-GFP- and wild-type H2R-expressing HEK-293 cells, both of which had constitutive activity of adenylate cyclase. Visualization of H2R-GFP revealed that the agonist-induced H2R internalization and the antagonist-induced recycling of the internalized H2R from the recycling endosome within 2 h. Long exposure to the antagonist increased GFP fluorescence in the plasma membrane and also induced upregulation of H2R-GFP estimated by the binding assay, whereas long exposure to the agonist enhanced degradative trafficking of H2R-GFP. We examined whether the upregulation reflected an increase in receptor synthesis. Treatment with antagonist did not augment H2R mRNA, and subsequent inhibition of protein synthesis by cycloheximide had no effect on H2R upregulation. These findings suggested that upon exposure to an antagonist (inverse agonist), the equilibrium between receptor endocytosis and recycling is altered before H2R upregulation, probably via suppressing H2R degradation.