Histamine2-receptor antagonists. Standard therapy for acid-peptic diseases. 1

Antacid Therapy in Coronary Artery Disease and Heart Failure: Proton Pump Inhibitors vs. H2 Receptor Blockers

PURPOSE

Acid suppressive therapy using histamine H2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) can be utilized for the prevention of gastrointestinal bleeding (GIB) among patients with cardiovascular disease receiving dual antiplatelet therapy (DAPT). However, emerging data suggests underlying associations between PPI or H2RA use and cardiovascular disease incidence, progression, and mortality. This review explores the history of acid suppressive therapies and their use in cardiovascular disease patients and the growing evidence in support of H2RA use.

RECENT FINDINGS

PPIs were originally championed as better than H2RAs for preventing GIB events in cardiovascular disease patients on DAPT therapy, but there is evidence to suggest that drug-drug interactions between clopidogrel and PPIs may translate to worse cardiovascular outcomes. Studies demonstrating PPI superiority in the setting of DAPT were also limited due to small sample sizes and high levels of bias. Consequently, there is renewed interest in H2RAs for patients on DAPT with some data demonstrating similar or improved clinical outcomes over PPI therapy. Additionally, studies have discovered a possible role for H2RAs in the management of heart failure (HF) incidence, symptoms, and mortality. Studies comparing H2RAs and PPIs in patients on DAPT have demonstrated mixed results for cardiovascular and GIB outcomes, with several studies being underpowered and limited by biases. Recent clinical and pre-clinical studies now support the noninferiority of H2RAs for major outcomes and even utility in HF. These findings suggest that H2RAs may warrant reconsideration as an acid suppressive therapy over PPIs for patients on DAPT or with HF.

Gastroprotective Effects of Fermented Gold Kiwi (Actinidia chinenesis L.) Extracts on HCl/EtOH-Induced Gastric Injury in Rats

Gastritis and gastric ulcers caused by stressors such as drinking are common. The ability of functional foods to protect the stomach more effectively and reduce the risk of side effects is of interest. The fermentation process can increase the preservation and bioactive compound content of kiwi fruits. This study produced fermented kiwi powder using two lactic acids separated from gold kiwi fruits. Gold kiwi puree (Actinidia chinensis L.) was fermented using beneficial bacteria. Fermentation increased the content of bioactive compounds such as organic acids, flavonoids, and carotenoids. We investigated whether fermented gold kiwi (FGK) extract had antioxidant and gastric protective effects in an HCl/EtOH-induced gastritis animal model and pyloric ligation animal model. FGK increased radical scavenging activity in a dose-dependent manner. In the gastritis model, FGK inhibited inflammation-related factors such as iNOS, COX-2, IL-6, and TNF-α, while increasing the expression of the protective molecule PGE2. Furthermore, FGK administration improved gastric lesion site appearance, clinical symptoms, and mucosal thickness in rats. FGK also reduced gastric fluid volume, free acidity, total acidity, and pepsin activity in the pyloric ligation model. These results suggest that FGK can decrease the inflammatory response and protect the gastric mucosa. FGK therefore has the potential to prevent and treat gastritis and gastric ulcers.

Pharmacokinetics and Bioequivalence Studies of Roxatidine Acetate Hydrochloride Sustained-Release Capsule in Healthy Chinese Subjects

This study aimed to evaluate the bioequivalence between a generic roxatidine acetate hydrochloride (RAH) sustained-release capsule and brand-named formulation (ALTAT) under fasting and fed conditions. An open-label, single-center, randomized 2-period crossover study with a 5-day washout period was conducted. A single oral dose of 75-mg generic RAH sustained-release capsule (test drug) or a commercial capsule (reference drug) was given to healthy volunteers under fasting (n = 36) and fed conditions (n = 36). Blood samples were collected at baseline and during the 24 hours after dosing. The concentrations of roxatidine acetate (ROX) and bioactive metabolite roxatidine in plasma were detected using a validated high-performance liquid chromatography-tandem mass spectrometry method. Pharmacokinetic parameters were analyzed with noncompartmental methods. As prodrug, RAH was dehydrochloric acid to ROX in body and further rapidly converted to roxatidine. Such a rapid metabolism resulted in ROX that was hardly detected in plasma. Active metabolism roxatidine was therefore used to evaluate the pharmacokinetic process. The major pharmacokinetic parameters of roxatidine including peak plasma concentration, area under the plasma concentration-time curve from time 0 to time t, and area under the plasma concentration-time curve from time 0 to infinity were similar between the 2 preparations under fasting and fed conditions. The generic RAH sustained-release capsule is bioequivalent to the reference drug under fasting and fed conditions in healthy Chinese subjects.

Rabeprazole: A comprehensive profile

Rabeprazole belongs to the class of anti-secretory drugs, with benzimidazoles substitution. These drugs induce gastric acid secretion through precise inhibition of the enzyme H⁺/K⁺-ATPase (acid or proton pump). This effect helps to treat and prevent conditions in which gastric acid directly aggravates symptoms such as duodenal and gastric ulcers. This chapter includes a comprehensive review of rabeprazole in terms of nomenclature, its physical-chemical properties, methods of preparation and ADME profiles. In addition, the chapter also includes a review of several methods for analysis of rebeprazole in its dosage forms and biological fluids.

Clopidogrel drug interactions: a review of the evidence and clinical implications

INTRODUCTION

Patients with cardiovascular disease are commonly affected by a number of comorbidities leading to a high prevalence of polypharmacy. Polypharmacy increases the probability of drug-drug interactions (DDIs). Amongst these, DDIs involving clopidogrel, the most commonly utilized platelet P2Y₁₂ inhibitor, is a topic of potential clinical concern.

AREAS COVERED

This article reviews DDIs between clopidogrel and drugs which are widely used in clinical practice. In particular, drugs shown to interfere with the pharmacodynamic and pharmacokinetic effects of clopidogrel and the clinical implications of these findings are reviewed. These drugs include inhibitors of gastric acid secretion, statins, calcium channel blockers, antidiabetic agents, and antimicrobial agents. For the references, we searched PubMed, EMBASE, or the Cochrane Library.

EXPERT OPINION

Clopidogrel-drug interactions are common. Most of these DDIs are limited to laboratory findings showing an impact on clopidogrel-induced antiplatelet effects. While variability in clopidogrel-induced antiplatelet effects is known to affect clinical outcomes, with high platelet reactivity being associated with thrombotic complications among patients undergoing coronary stenting, most studies assessing the clinical implications of clopidogrel-drug interactions have not shown to significantly affect outcomes. However, awareness of these DDIs remains important for optimizing the selection of concomitant therapies.

Comparative Evaluation of Antiulcer Activity of Ficus religiosa (Stem Bark) Extracts Prepared by Different Methods of Extraction

Background:

The stem bark of Ficus religiosa L. (Family-Moraceae) is traditionally used to treat gonorrhea, diarrhea, dysentery, leucorrhea, menorrhagia, vaginal and other urogenical disorders, ulcers and gastrohelcosis.

Objective:

The study was aimed at comparing antiulcer activity (ethanol induced gastric ulcer) for stem bark extracts of Ficus religiosa Linn. prepared by different extraction methods viz. soxhlet, ultrasonication and microwave assisted extraction.

Methods:

The powdered drug material was extracted by soxhlet (time 48 hours., temperature 60°C and solvent 60% ethanol), Ultrasonic (90 min., 50°C and acetone as solvent)and Microwave (3 min., 60°C and acetone as solvent) assisted extraction method. The acute toxicity study was carried out in adult female albino rats by “fix dose” method of OECD guideline no. 420 for selection of doses. Antiulcerogenic effect of prepared extracts (200mg/kg) was evaluated by ethanol induced ulcer method using omeprazole (40 mg/kg) as standard drug and absolute alcohol 99.5% as necrotizing agent.

Result and Conclusion:

Acute toxicity study did not show any significant toxicity signs and extracts were said to be practically non-toxic at tested dose level of 2000 mg/kg, b.w. The best antiulcer activity was shown by the hydroalcoholic extract prepared by soxhlet extraction method. Administration of ethanol produced significant ulcer index (41.00 ± 1.75) in the control group. Standard drug omeprazole (40 mg/kg) produced percentage protection of 70.31%. Among all three extracts, Ulcer index is significantly (p<0.001) protected by hydroalcoholic extract (Soxhlet Extraction Method) with percentage protection 52.02%.

Cytoprotective and antisecretory properties of methanolic extract of Distemonanthus benthamianus (Caesalpiniaceae) stem bark on acute gastric ulcer in rats

OBJECTIVES

In African traditional medicine, Distemonanthus benthamianus (Caesalpiniaceae) is used to treat many diseases including gastric ulcers. We evaluated in this study, the cytoprotective and antisecretory properties of the methanolic extract of the stem bark of this plant using different technics of gastric lesion induction.

METHODS

Cytoprotective and antisecretory activity of the methanolic extract of D. benthamianus stem bark was evolved through six methods of gastric lesion induction in experimental Wistar male rats (150-200 g): (1) gastric lesions induced by HCl/ethanol, (2) gastric lesions induced by Indomethacin- HCl/ethanol, (3) gastric lesion induced by Indomethacin, (4) gastric lesions induced by Pylorus ligation, (5) gastric lesions induced by histamine-Pylorus ligation, (6) gastric lesions induced by carbachol-Pylorus ligation. Mucus and gastric mucosal ulceration were evaluated. pH, gastric volume, and acidity were quantified in all pylorus ligation induction technics. Nitric oxide (NO) level was determined in indomethacin induced gastric ulcers.

RESULTS

At different doses (125, 250 and 500 mg/kg), extract reduced significantly the ulcer index. In all models used, that is 100.00% with HCl/ethanol; 100.00% with HCl/ethanol/indomethacin; 95.70% with Indomethacin; 74.79% with pylorus ligation, 95.94% histamine-Pylorus ligation, 99.54% carbachol-Pylorus ligation at the highest dose of 500 mg/kg. The lesion formation reduces in all the methods used followed by a significant increase of mucus production. The pylorus ligation technic revealed that the extract has an antisecretory activity.

CONCLUSIONS

The methanolic extract of D. benthamianus stem bark has both cytoprotective and antisecretory effects. This extract exerts its antisecretory effect trough cholinergic and histaminergic pathways.

Gastroprotective and Ulcer Healing Effects of Camel Milk and Urine in HCl/EtOH, Non-steroidal Anti-inflammatory Drugs (Indomethacin), and Water-Restraint Stress-induced Ulcer in Rats

Background:

Camel milk has been reportedly used to treat dropsy, jaundice, tuberculosis, and diabetes while camel urine is used to treat diarrhea and cancer. However, there is no scientific evidence on the antiulcer activity of camel milk and urine. Thus, the present is designed to investigate the gastroprotective and ulcer healing effect of camel milk and urine on experimentally induced gastric ulcer models in rats.

Materials and Methods:

The gastroprotective effect was investigated in HCl/EtOH, water-restraint stress (WRS) and non-steroidal anti-inflammatory drugs (indomethacin)-induced ulcer models while ulcer healing activity was investigated in indomethacin-induced ulcer model. Cimetidine (100 mg/kg) was used as a standard antiulcer drug.

Results:

Acute toxicity study done up to a dosage of 10 ml/kg of camel milk and urine showed no signs of toxicity and mortality among the rats, indicating the present dosage of 5 ml/kg is safe to be administered to the rats. In the HCl/EtOH model, oral administration of cimetidine (100 mg/kg), camel urine (5 ml/kg), and camel milk (5 ml/kg) significantly (P < 0.05) inhibited gastric lesions by 83.7, 60.5 and 100%, respectively. In the WRS-induced model, cimetidine, and camel urine showed an ulcer inhibition of 100% while camel milk showed an inhibition of 50%. Similarly, in the indomethacin-induced ulcer model, cimetidine, camel milk, and urine showed an ulcer inhibition of 100, 33.3, and 66.7%, respectively. In addition, camel milk and urine also showed a significant (P < 0.05) ulcer healing effect of 100% in indomethacin-induced ulcer model, with no ulcers observed as compared to that of cimetidine, which offers a healing effect of 60.5%.

Conclusion:

The antiulcer activity of camel milk and urine may be attributed to its cytoprotective mechanism and antioxidant properties.

SUMMARY

Acute toxicity findings revealed the dosage of 10 ml/kg of camel milk and urine seems no toxic and indicating the dosage of 5 ml/kg is safe to be administered to the rats

Oral administration of cimetidine (100 mg/kg), camel urine (5 ml/kg), and camel milk (5 ml/kg) significantly inhibited gastric lesions by 83.7, 60.5 and 100% in the HCl/EtOH experimental model

The results of this investigation have proven that camel milk and urine showed strong ulcer healing effect in indomethacin-induced gastric damage.

Abbreviations used: NSAIDs: Non-steroidal anti-inflammatory drugs, UI: Ulcer index, ANOVA: One-way analysis of variance, WRS: Water-restraint stress, ROS: Reactive oxygen species

Docking-based Screening of Ficus religiosa Phytochemicals as Inhibitors of Human Histamine H2 Receptor

Background:

Ficus religiosa L. is generally known as Peepal and belongs to family Moraceae. The tree is a source of many compounds having high medicinal value. In gastrointestinal tract, histamine H2 receptors have key role in histamine-stimulated gastric acid secretion. Their over stimulation causes its excessive production which is responsible for gastric ulcer.

Objective:

This study aims to screen the range of phytochemicals present in F. religiosa for binding with human histamine H2 and identify therapeutics for a gastric ulcer from the plant.

Materials and Methods:

In this work, a 3D-structure of human histamine H2 receptor was modeled by using homology modeling and the predicted model was validated using PROCHECK. Docking studies were also performed to assess binding affinities between modeled receptor and 34 compounds. Molecular dynamics simulations were done to identify most stable receptor-ligand complexes. Absorption, distribution, metabolism, excretion, and screening was done to evaluate pharmacokinetic properties of compounds.

Results:

The results suggest that seven ligands, namely, germacrene, bergaptol, lanosterol, Ergost-5-en-3beta-ol, α-amyrin acetate, bergapten, and γ-cadinene showed better binding affinities.

Conclusion:

Among seven phytochemicals, lanosterol and α-amyrin acetate were found to have greater stability during simulation studies. These two compounds may be a suitable therapeutic agent against histamine H2 receptor.

SUMMARY

This study was performed to screen antiulcer compounds from F. religiosa. Molecular modeling, molecular docking and MD simulation studies were performed with selected phytochemicals from F. religiosa. The analysis suggests that Lanosterol and α-amyrin may be a suitable therapeutic agent against histamine H2 receptor. This study facilitates initiation of the herbal drug discovery process for the antiulcer activity.

Abbreviations used: ADMET: Absorption, distribution, metabolism, excretion and toxicity, DOPE: Discrete Optimized Potential Energy, OPLS: Optimized potential for liquid simulations, RMSD: Root-mean-square deviation, HOA: Human oral absorption, MW: Molecular weight, SP: Standard-precision, XP: Extra-precision, GPCRs: G protein-coupled receptors, SASA: Solvent accessible surface area, Rg: Radius of gyration, NHB: Number of hydrogen bond

Proton Pump Inhibitors and Survival Outcomes in Patients With Metastatic Renal Cell Carcinoma

INTRODUCTION

Proton pump inhibitors (PPIs) are potent inhibitors of gastric acid secretion and can affect the optimal absorption of concomitant oral medications, such as vascular endothelial growth factor (VEGF) tyrosine kinase inhibitors (TKIs). The purpose of this study was to investigate the effect of PPI use on survival in metastatic renal cell carcinoma (mRCC) patients treated in the targeted therapy era.

MATERIALS AND METHODS

We conducted a pooled analysis of mRCC patients treated in phase II and III clinical trials. Statistical analyses were performed using Cox regression adjusted for several risk factors and the Kaplan-Meier method.

RESULTS

We identified 2188 patients treated with sunitinib (n = 952), axitinib (n = 626) or sorafenib (n = 610), of whom 120 were PPI users. Overall, PPI users showed similar overall survival compared with non-PPI users (hazard ratio [HR], 1.051; 95% confidence interval [CI], 0.769-1.438; P = .754; median, 24.1 vs. 21.3 months). Similarly, progression-free survival (HR, 1.016; 95% CI, 0.793-1.301; P = .902; median, 5.5 vs. 8.0 months) and objective response rates (23.3% vs. 27.4%; P = .344) were not different between PPI users and nonusers. These findings were consistent across International mRCC Database Consortium risk groups and according to line of therapy. Adverse events were similar between PPI users and nonusers.

CONCLUSION

We showed that PPI use does not appear to negatively affect the efficacy and safety of select VEGF-TKIs in patients with mRCC. Documentation of concomitant medications and patient education on potential drug interactions are critical for optimizing the use of oral cancer-targeting therapy.

Histamine-2 Receptor Antagonist Cannot Prevent Recurrent Peptic Ulcers in Patients With Atherosclerotic Diseases Who Receive Platelet ADP Receptor Antagonist Monotherapy: A Randomized-Controlled, Double-Blind, and Double-Dummy Trial

OBJECTIVES

Proton pump inhibitor can effectively prevent recurrent peptic ulcers among atherosclerotic patients receiving clopidogrel monotherapy. However, the interaction between proton pump inhibitors and clopidogrel has raised concerns over the safety of combined use of the two medicines in clinical practice. The aims of this randomized-controlled, double-blind and double-dummy trial were to investigate the efficacy of histamine-2 receptor antagonist (H2RA) in the prevention of recurrent peptic ulcer in patients undergoing thienopyridine monotherapy.

METHODS

From January 2012 to 2016, long-termed thienopyridine users with a peptic ulcer history who did not have peptic ulcers at initial endoscopy were randomly assigned to receive either famotidine (40 mg, before bedtime) or placebo (before bedtime) for 6 months. Follow-up endoscopy was performed at the end of the 6th month and whenever dyspepsia, hematemesis, or melena occurred.

RESULTS

The cumulative incidence of recurrent peptic ulcer during the 6-month period was 7.0% in famotidine group (n=114) and 11.4% in the placebo group (n=114). The two patient groups had comparable cumulative incidence of peptic ulcer (difference, 4.4%; 95% confidence interval (CI), -11.7 to 2.9%; P=0.239). Additionally, there was no difference in the cumulative incidence of ulcer bleeding (2.6% vs. 1.8%; difference, 0.8%; 95% CI, -0.6 to 2.4%, P=1.000) between famotidine and placebo groups. However, the former had a lower incidence of gastroduodenal erosion than the latter (21.1% vs. 36.8%; difference, 15.7%; 95% CI, -27.3 to -4.1%; P=0.013).

CONCLUSIONS

Famotidine cannot decrease the incidence of peptic ulcer or ulcer bleeding in thienopyridine users with atherosclerotic disease and a history of peptic ulcer.

Gastroduodenal Ulceration in Small Animals: Part 2. Proton Pump Inhibitors and Histamine-2 Receptor Antagonists

In the first part of this review, we discussed the pathophysiology and epidemiology of gastric acid secretion and the epidemiology of gastroduodenal ulceration in dogs and cats. In this section, we discuss the pharmacology and evidence-based clinical use of histamine-2 receptor antagonists and proton pump inhibitors.

Current Status of Gastric Proton Pump Inhibitors in the Treatment of Acid-Peptic Disease

Proton pump inhibitors represent an important advance in the treatment of acid-peptic disease. Omeprazole, the prototype of the drug class, produces a profound and sustained degree of gastric acid suppression. Recent studies confirm earlier reports that omeprazole 20 mg/d is generally more effective than standard histamine2 receptor antagonist (H2RA) dosage regimens in treating duodenal ulcer (DU), gastric ulcer (GU), and erosive esophagitis. Omeprazole tends to accelerate DU and GU healing, especially during the first 2 weeks of treatment, and also accelerates mucosal healing in patients with all grades of esophagitis. Omeprazole is the drug of choice for treating patients with large or refractory ulcers, severe or refractory erosive esophagitis, Barrett's esophagus, and Zollinger-Ellison syndrome. Maintenance therapy with omeprazole seems to reduce ulcer recurrence and esophagitis, but optimal treatment regimens must be established. Dual therapy with omeprazole and amoxicillin shows encouraging results in eradicating Helicobacter pylori, reducing duodenal ulcer recurrence rates, and altering the natural history of peptic ulcer disease. Further studies are required to determine the efficacy of omeprazole in preventing nonsteroidal anti-inflammatory drug-induced ulcers and stress-related mucosal bleeding, and in treating upper gastrointestinal bleeding. Omeprazole is well-tolerated in the majority of patients receiving either short-term or long-term treatment. The type and frequency of adverse effects are similar to those reported with the H2RAs. There is no evidence to support genotoxicity or hypergastrinemia-induced enterochromaffin-like cell carcinoid of the stomach in patients receiving omeprazole treatment for more than 5 years. Omeprazole interacts selectively with hepatic P-450 and may potentially interact with phenytoin, warfarin, or diazepam. Pharmacoeconomic studies suggest that treatment with omeprazole provides a significant cost-savings over the H2RAs in patients with moderate to severe erosive esophagitis and possibly in patients with DU. Lansoprazole, a newly developed proton pump inhibitor, seems to offer no clear advantage over omeprazole.

Reducing the Use of H2-Receptor Antagonists in the Long-Term-Care Setting

OBJECTIVES

To examine the patterns of H2 blocker use in the long-term-care setting and to assess the effect of educational interventions designed to improve H2 blocker utilization patterns.

DESIGN

Time-series quasi-experimental study and retrospective chart review.

SETTING

A large academically-oriented long-term-care facility.

PATIENTS

Institutionalized elderly patients with a mean age of 88 years receiving H2 blocker therapy.

INTERVENTIONS

Two interventions involving group discussions with the medical staff, supporting educational materials, and physician-specific listings of patients receiving H2 blockers were employed sequentially over a 32-month period.

RESULTS

Each intervention resulted in substantial reductions in medication use (59.6% and 32.1%, respectively). Indications for H2 blocker use were determined retrospectively for patients identified as receiving therapy prior to the interventions (n = 110). Forty-one percent were found to be receiving therapy for reasons unsubstantiated by the medical literature. These patients were more likely to be discontinued from therapy than those receiving therapy for substantiated indications (P less than 0.01), consistent with the primary focus of the educational interventions.

CONCLUSIONS

These results suggest that the excessive use of H2 blocker therapy in the long-term care setting responds to educational interventions with therapeutically appropriate reductions in utilization. Repeated interventions are necessary to maintain such reductions over time although there may be some reduction in the effectiveness of the intervention with repetition.

Anti-gastritis and wound healing effects of Momordicae Semen extract and its active component

Momordicae Semen, Momordica cochinchinensis Springer (Cucurbitaceae), has long been known to effectively relieve boils, rheumatic pain, and hemorrhoids. In this study, we investigated whether Momordicae Semen extract (MSE) has anti-gastritis effects in various rodent models and also explored possible mechanisms for the gastroprotective effects of MSE. MSE provided remarkable protective effects, comparable to those of rebamipide, in ethanol- and diclofenac-induced acute gastritis. In addition, it has demonstrated protective effect in a Helicobacter pylori-insulted chronic gastritis model. MSE also showed wound healing effect on cutaneous injury of mice and stimulated calcitonin gene-related peptide and somatostatin receptors, which may be related to its anti-gastritis effects. In a single oral dose toxicity study, the approximate lethal dose of MSE was determined at >2000 mg/kg/day. The NOAEL was set to be 2000 mg/kg/day from the repeated oral dose toxicity study. Moreover, momordica saponin I, a major ingredient of MSE, treatment decreased gastric mucosa damage indices in the ethanol- and diclofenac-induced acute gastritis models. The results suggest that MSE could be a promising gastroprotective herbal medicine and momordica saponin I might be used as an active marker compound for MSE.

A review of stress-related mucosal disease

OBJECTIVE

To review and summarize the human and veterinary literature regarding stress-related mucosal disease (SRMD) pathogenesis, patient risk factors, and therapeutic options for prophylaxis and treatment.

ETIOLOGY

SRMD is a common sequela of critical illness in human patients. Development of SRMD results from splanchnic hypoperfusion, reperfusion injury, and exposure of the gastric mucosa to acid, pepsin, and bile acids following breakdown of the gastric mucosal defense system. Human patients with the highest risk of stress ulceration include those with respiratory failure necessitating mechanical ventilation greater than 48 h or coagulopathy. Currently, little is known about the incidence and pathophysiology of SRMD in critically ill veterinary patients.

DIAGNOSIS

A presumptive diagnosis can be made in high-risk patient populations following detection of occult or gross blood in nasogastric tube aspirates, hematemesis, or melena. Definitive diagnosis is achieved via esophagogastroduodenoscopy. Lesions are localized to the acid-producing portions of the stomach, the fundus, and body.

THERAPY

Therapy is aimed at optimization of tissue perfusion and oxygenation. Pharmacologic interventions are instituted to increase intraluminal pH and augment natural gastric defenses. Histamine(2)-receptor antagonists, proton pump inhibitors, and sucralfate are the mainstays of therapy. In people, clinically significant bleeding may necessitate additional interventions (eg, packed red blood cell transfusions, endoscopic, or surgical hemostasis).

PROGNOSIS

Mortality is increased in people with clinically significant bleeding compared to those patients who do not bleed. Institution of prophylaxis is recommended in high-risk patients. However, no consensus exists regarding initiation of prophylaxis, preference of frontline drug class, or indication for discontinuation of therapy. The prognosis of veterinary patients with SRMD remains unknown at this time.

Esomeprazole compared with famotidine in the prevention of upper gastrointestinal bleeding in patients with acute coronary syndrome or myocardial infarction

OBJECTIVES

Little is known about the efficacy of proton pump inhibitors compared with H(2) receptor antagonists in preventing adverse upper gastrointestinal complications in patients with acute coronary syndrome (ACS) or ST elevation myocardial infarction (STEMI) receiving aspirin, clopidogrel, and enoxaparin or thrombolytics. The objective of this study was to compare the efficacies of esomeprazole and famotidine in preventing gastrointestinal complications.

METHODS

A double-blind, randomized, controlled trial was performed in patients receiving a combination of aspirin, clopidogrel, and either enoxaparin or thrombolytics. Patients received either esomeprazole (20 mg nocte) or famotidine (40 mg nocte) orally for 4-52 weeks, depending on the duration of dual antiplatelet therapy. The primary end point was upper gastrointestinal bleeding (GIB), perforation, or obstruction from ulcer/erosion (http://www.clinicaltrials.gov NCT00683111).

RESULTS

In all, 311 patients were recruited, with 163 and 148 patients in the esomeprazole and famotidine groups, respectively. Mean (s.d.) follow-up was 19.2 (17.6) and 17.6 (18.0) weeks, respectively. One (0.6%) patient in the esomeprazole group and 9 (6.1%) in the famotidine group reached the primary end point (log-rank test, P=0.0052, hazard ratio=0.095, 95% confidence interval: 0.005-0.504); all had upper GIB.

CONCLUSIONS

In patients with ACS or STEMI, esomeprazole is superior to famotidine in preventing upper gastrointestinal complications related to aspirin, clopidogrel, and enoxaparin or thrombolytics.

Deep Vein Thrombosis and Stress Ulcer Prophylaxis in the Intensive Care Unit

Deep vein thrombosis (DVT) and stress gastric ulcers can be serious complications in patients admitted to the intensive care unit. This review discusses the risk factors associated with the development of DVT and stress-related mucosal disease (SRMD), evaluates the available literature on current options for DVT and stress ulcer prophylaxis, and examines the associated adverse effects and optimal duration of therapy.

The H2 receptor antagonist nizatidine is a P-glycoprotein substrate: characterization of its intestinal epithelial cell efflux transport

The aim of this study was to elucidate the intestinal epithelial cell efflux transport processes that are involved in the intestinal transport of the H(2) receptor antagonist nizatidine. The intestinal epithelial efflux transport mechanisms of nizatidine were investigated and characterized across Caco-2 cell monolayers, in the concentration range 0.05-10 mM in both apical-basolateral (AP-BL) and BL-AP directions, and the transport constants of P-glycoprotein (P-gp) efflux activity were calculated. The concentration-dependent effects of various P-gp (verapamil, quinidine, erythromycin, ketoconazole, and cyclosporine A), multidrug resistant-associated protein 2 (MRP2; MK-571, probenecid, indomethacin, and p-aminohipuric acid), and breast cancer resistance protein (BCRP; Fumitremorgin C) inhibitors on nizatidine bidirectional transport were examined. Nizatidine exhibited 7.7-fold higher BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion. All P-gp inhibitors investigated displayed concentration-dependent inhibition on nizatidine secretion in both directions. The IC(50) of verapamil on nizatidine P-gp secretion was 1.2 x 10(-2) mM. In the absence of inhibitors, nizatidine displayed concentration-dependent secretion, with one saturable (J(max) = 5.7 x 10(-3) nmol cm(-2) s(-1) and K(m) = 2.2 mM) and one nonsaturable component (K(d) = 7 x 10(-4) microL cm(-2) s(-1)). Under complete P-gp inhibition, nizatidine exhibited linear secretory flux, with a slope similar to the nonsaturable component. V(max) and K(m) estimated for nizatidine P-gp-mediated secretion were 4 x 10(-3) nmol cm(-2) s(-1) and 1.2 mM, respectively. No effect was obtained with the MRP2 or the BCRP inhibitors. Being a drug commonly used in pediatrics, adults, and elderly, nizatidine susceptibility to efflux transport by P-gp revealed in this paper may be of significance in its absorption, distribution, and clearance, as well as possible drug-drug interactions.

Body mass index and the efficacy of acid-mediating agents for GERD

In studies of the association between obesity and gastroesophageal reflux, one subject that has received very little attention is the effect excess body mass may have on the effectiveness of acid-mediating agents. The lack of systematic research may reflect the perceived high clinical efficacy of drugs like proton pump inhibitors. Both proton pump inhibitors and histamine type 2 receptor antagonists have low rates of significant adverse events; if there are differences in the side effect profiles based on BMI, it is unlikely such associations would be detected. Also, while the metabolism of many drugs can be affected by body mass, it is not clear that such a relationship exists with acid-mediating agents. Nevertheless, there is evidence that body mass index may indeed be associated with the efficacy of proton pump inhibitors and histamine type 2 receptor antagonists. This review will examine that evidence and consider some of the possible pharmacokinetic effects that might relate to body mass index.

Histamine mediates osteoclastic resorption only during the acute phase of bone loss in ovariectomized rats

Short-term studies have shown that histamine is involved, via its H2 receptors (H2R), in the mediator network regulating trabecular bone loss in long bones of ovariectomized (OVX) rats. It is not known whether this effect of histamine persists over time or involves other skeletal sites. In this study, rats were maintained for 6 months postOVX and treated daily with saline or famotidine (10 mg kg(-1)), an H2R antagonist. At the end of the experimental period, femur trabecular bone mass was markedly decreased in OVX rats, whether or not they were treated with famotidine. In contrast, in the fourth lumbar vertebra, where bone loss starts later than in the femur, famotidine treatment attenuated the decline in trabecular bone volume, protected the trabecular architecture, maintained the thickness of the cortices and reduced the numbers of osteoclasts and tartrate-resistant acid phosphatase-positive preosteoclasts, whereas it had no influence on bone formation parameters. In vertebral bone marrow of OVX rats, the numbers of mast cells (MCs) and non-MC histamine-producing cells increased, while famotidine treatment significantly diminished both cell populations. These data show that H2R antagonism does not protect trabecular bone mass in the long term, and that short-term protection involves all bones. Histamine is involved during the early phase of strong osteoclastic resorption but not during the late phase of slower resorption, suggesting that different mediator networks control the two phases of destruction. Histamine would be part of the network mediating the early phase.

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.

Pathophysiology and prophylaxis of stress ulcer in intensive care unit patients

Gastrointestinal complications frequently occur in patients admitted to the intensive care unit. Of these, ulceration and bleeding related to stress-related mucosal disease (SRMD) can lengthen hospitalization and increase mortality. The purpose of this review is to discuss the many risk factors and underlying illnesses that have a role in the pathophysiology of SRMD and evaluate the evidence pertaining to SRMD prophylaxis in the intensive care unit population. Suppressing acid production is fundamental to preventing stress-related mucosal ulceration and clinically important gastrointestinal bleeding. Traditional prophylactic options for SRMD in critically ill patients include antacids, sucralfate, histamine 2 -receptor antagonists (H 2 RAs), and proton pump inhibitors. Many clinicians prescribe intermittent infusions of H 2 RAs for stress ulcer prophylaxis, a practice that has not been approved for this indication and may not provide the necessary degree or duration of acid suppression required to prevent stress ulcer-related bleeding. New data suggest that proton pump inhibitors suppress acid production more completely in critically ill patients, but more studies are required to assess their clinical effectiveness and safety for this indication. The prophylactic regimen chosen to prevent stress ulcer bleeding should take into account the risk factors and underlying disease state of individual patients to provide the best therapy to those most likely to benefit.

Nondiarrheal Disorders of the Gastrointestinal Tract in Neonatal Foals

Neonates can have a variety of gastrointestinal disorders, primary and secondary in nature. Important primary disorders include con-genital abnormalities and meconium retention. One of the most important secondary lesions is generalized ileus. Gastric ulceration can occur as a primary or secondary event. This article addresses the pathophysiology, diagnosis, and treatment of gastrointestinal problems commonly observed in neonatal foals.

Bioequivalence of two oral formulations of nizatidine capsules in healthy male volunteers

PURPOSE

The purpose of this randomized, crossover study was to compare the bioavailability of a generic and an innovator formulation of nizatidine 300 mg capsules under fasting conditions.

METHODS

Twenty blood samples per period were collected from 20 healthy, Arab male volunteers over 16 h, plasma nizatidine concentrations were determined by HPLC assay, and pharmacokinetic parameters were determined by the non-compartmental method.

RESULTS

Mean+/-SD C(max), T(max), AUC(0-->t), AUC(0-->infinity), and t1/2 were 2.96+/-0.54 and 3.28+/-0.68 microg/ml, 1.31+/-0.70 and 0.93+/-0.38 h, 9.04+/-1.66 and 9.03+/-1.94 microg x h/ml, 9.17+/-1.64 and 9.12+/-1.94 microg x h/ml, and 1.64+/-0.21 and 1.58+/-0.22 h for the generic and innovator formulation, respectively. The parametric 90% confidence intervals on the mean of the difference between log-transformed values were 98.06% to 103.21%, 98.74% to 103.71%, and 83.37% to 101.34%, for AUC(0-->t), AUC(0-->infinity), and C(max), respectively.

CONCLUSION

The results indicate that these two formulations are equivalent in the rate and extent of absorption.

Overview of pharmacologic agents for acid suppression in critically ill patients

PURPOSE

The physiology of acid secretion, rationale and goals for acid suppression in critically ill patients, and mechanism of action, pharmacokinetics, pharmacodynamics, and safety of histamine H2-receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) are discussed.

SUMMARY

Acid-suppressant therapy may be used in critically ill patients to prevent stress-related mucosal disease or the recurrence of peptic ulcer bleeding. The intragastric pH goal is 3.5-4.5 and 6 or higher, respectively. H2RAs block only one of three pathways in acid secretion and provide less potent acid suppression than PPIs, which block the final common pathway in acid secretion. In addition, tolerance that occurs with H2RAs does not occur with PPIs. All PPIs work in a similar manner, but differences exist in the pharmacokinetic profiles and binding to the proton pump; the clinical relevance of these differences remains debated. The safety profiles of H2RAs and PPIs are similar; however, the H2RA dose, but not the PPI dose, must be adjusted for patients with renal dysfunction. The risk of drug interactions mediated by cytochrome P-450 enzymes is lower with PPIs than with cimetidine, an H2RA. Several new PPI dosage forms have been introduced, facilitating drug administration in the critical care setting.

CONCLUSION

Both H2RAs and PPIs are safe agents to use for providing acid suppression in critically ill patients, but PPIs offer several potential advantages over H2RAs.

Cimetidine and Other Histamine2-Receptor Antagonist Use in Relation to Risk of Breast Cancer

OBJECTIVE

Cimetidine, a histamine2-receptor antagonist (H2 blocker) commonly used to treat symptoms of peptic and duodenal ulcer, influences both hormonal and immune pathways. We investigated the influence of cimetidine use on the risk of breast cancer in our hospital-based case control surveillance study.

METHODS

Data on medication use and other factors were elicited from patients admitted to hospitals from 1977 to 2002. We compared 6,994 breast cancer cases with a control group comprising cancer (n = 2,478) and noncancer (n = 6,004) diagnoses. Conditional logistic regression models were used to estimate odds ratios for H2 blocker use that began at least 1 year prior to admission. Regular use was defined as use for at least 4 days per week for at least 3 continuous months.

RESULTS

The odds ratio for breast cancer among regular users of cimetidine was 0.9 (95% confidence interval, 0.6-1.2) using a combined cancer and noncancer control group. For use of 4 or more years' duration, the odds ratio was < 1.0 but was not statistically significant. The odds ratio for the regular use of other H2 blockers was 0.9 (95% confidence interval, 0.6-1.3).

CONCLUSIONS

Our data agree with data from three prior studies which indicate that cimetidine is not associated with the risk of breast cancer. Other H2 blockers were also unrelated to the risk of breast cancer.

Histamine participates in the early phase of trabecular bone loss in ovariectomized rats

We have previously reported that cimetidine, a reference H2 receptor antagonist, attenuates the initial osteoclastic burst and subsequent trabecular bone loss induced by ovariectomy (ovx) in rats. This study was designed to determine whether these effects are specific to H2 antagonism. To this end, we compared the effects of two H2 receptor antagonists, cimetidine and famotidine. In addition, we analyzed the response of histamine-producing cells to these inhibitors. Seventy-two 90-day-old female Sprague-Dawley rats were ovariectomized or sham-operated, and received single daily intramuscular injections of cimetidine (125 mg/kg), famotidine (10 mg/kg), or vehicle. The animals were killed 14 days after surgery and their femurs were processed for histomorphometry. Trabecular bone volume was reduced by 30% in ovx rats and by 15% in cimetidine- and famotidine-treated rats. Architectural parameters were reduced by about 20% in ovx rats. Cimetidine and famotidine attenuated these consequences of ovx by about 50%. Trabecular connectivity was deteriorated by ovx, while cimetidine and famotidine attenuated this effect. Resorption parameters were increased by ovx, while cimetidine and famotidine prevented this increase. Kinetic bone formation parameters were increased by ovx, while cimetidine and famotidine had no influence. Neither cimetidine nor famotidine had any observable effect in sham-treated rats. Mast cell numbers increased by 250% in ovx rats and by only 40% in H2 antagonists-treated ovx rats. A resident histamine-positive, non-mast cell, population found in bone marrow was increased by 25% by ovx. Interestingly, cimetidine and famotidine reduced this population in both sham-operated and ovx rats, famotidine being more potent than cimetidine. These results show that H(2) receptor blockade partially prevents the consequences of castration on cancellous bone resorption in female rats, and strongly suggest that histamine participates in the mediator network regulating estrogen deficiency induced bone resorption. A large population of histamine-producing cells, which differ morphologically from mast cells and belong to an immature marrow population, may be a source of histamine in this model. The H(2) blockers targeted this population, and this effect appeared to explain the anti-resorptive action of the two drugs.

Gastrointestinal disease control after histamine2-receptor antagonist dose modification for renal impairment in frail chronically ill elderly patients

OBJECTIVES

To determine whether histamine2-receptor antagonist (H2RA) dose modified for renal impairment affects gastrointestinal (GI) disease control.

DESIGN

Concurrent medical record review.

SETTING

One hundred forty-six nursing facilities throughout the United States.

PARTICIPANTS

Three hundred thirty-six patients aged 65 and older receiving H2RAs for GI disorders.

INTERVENTION

H2RA dose modified for renal impairment or no dose change.

MEASUREMENTS

Disease control (no H2RA dose increase for 6 months or longer, additional GI medication, hospitalizations, emergency room visits, and unscheduled physician visits for GI symptoms) was evaluated using chart review at 3, 6, 9, and 12 months in nursing home patients aged 65 and older with H2RA dose modified for decreased creatinine clearance (ClCr) according to manufacturer.

RESULTS

Three hundred thirty-six patients, mean age +/- standard deviation 85.9 +/- 7.9, with mean ClCr of 33.6 +/- 10.4 mL/min, were recommended to receive lower H2RA doses based upon estimated renal function. Patients were analyzed in two groups: H2RA dose reduced (Group 1) and dose reduction not adopted or implemented (Group 2). There was no difference in baseline characteristics (age, weight, ClCr, or starting H2RA dose and indication) between the two groups. One hundred ninety-eight patients in Group 1 were taking 195.5 +/- 71.0 mg per day of nizatidine or equivalent, compared with 183.7 +/- 66.6 mg for 138 patients in Group 2. For patients with 90 days of follow-up, the mean H2RA dose in Group 1 was 100.2 +/- 44.3 mg, compared with 187.8 +/- 69.9 for Group 2 (P <.0001) The mean decrease in daily dose for Groups 1 and 2 after 365 days were 98.9 +/- 72.9 mg and 22.2 +/- 68.2 mg, respectively (P <.0001). Except for more physician visits in Group 2, disease control was similar for all groups. Major and minor GI bleeding events were similar across both groups and over time. The 12-month mortality rate was 12.1% and 21.7% for Groups 1 and 2, respectively. This difference was statistically significant (P =.02).

CONCLUSION

The findings suggest that the dose of H2RAs may be decreased based upon renal function in frail elderly patients without compromising GI disease control.

Gastric cytoprotective anti-ulcer effects of the leaf methanol extract of Ocimum suave (Lamiaceae) in rats

The anti-ulcerogenic potential of the leaf methanol extract of Ocimum suave (Lamiaceae) was investigated using four methods of gastric lesion induction in experimental Wistar rats (150-200 g): (1) HCl/ethanol-induced gastric lesions, (2) Absolute ethanol-induced gastric lesions, (3) Indomethacin-HCl/ethanol-induced gastric lesions, (4) Pylorus ligation-induced gastric lesions. Administration of the extract of O. suave to the rats by oral route (75-500 mg/kg) dose-dependently prevented the formation of acute gastric lesions induced using the four experimental techniques. The dose-dependent reduction of lesion formation was in all cases accompanied by significant increases in gastric mucus production. At the dose of 250 mg/kg there was complete inhibition of gastric lesions induced using the HCl/ethanol solution. Pre-treatment, by intraperitoneal route, with indomethacin significantly reduced the ability of the extract to inhibit the formation of HCl/ethanol-induced lesions. When the rats were subjected to pylorus ligation, the dose of 500 mg/kg completely inhibited lesion formation but did not have any effect on gastric acid secretion compared with the controls. The mucus secretion promoting effect of the extract was most significant when the gastric environment was highly acidic. These results suggest that a new anti-ulcer therapy regimen may be formulated which does not require the use of antacids and anti-secretory agents.

Molecular cloning and pharmacology of functionally distinct isoforms of the human histamine H(3) receptor

The pharmacology of histamine H(3) receptors suggests the presence of distinct receptor isoforms or subtypes. We herein describe multiple, functionally distinct, alternatively spliced isoforms of the human H(3) receptor. Combinatorial splicing at three different sites creates at least six distinct receptor isoforms, of which isoforms 1, 2, and 4, encode functional proteins. Detailed pharmacology on isoforms 1 (unspliced receptor), and 2 (which has an 80 amino acid deletion within the third intracellular loop of the protein) revealed that both isoforms displayed robust responses to a series of known H(3) agonists, while all agonists tested displayed increased potency at isoform 2 relative to isoform 1. Histamine, N(alpha)-methylhistamine, and R(-) and S(+)-alpha-methylhistamine are 16-23-fold more potent, while immepip and imetit are three to fivefold more potent. Antagonist experiments revealed a rank order of potency at both isoforms of clobenpropit>iodophenpropit>thioperamide, and these drugs are fivefold less potent at isoform 2 than isoform 1. To further explore the pharmacology of H(3) receptor function, we screened 150 clinically relevant neuropsychiatric drugs for H(3) receptor activity, and identified a small number of antipsychotics that possess significant antagonist activity.

Cimetidine modulates the antigen presenting capacity of dendritic cells from colorectal cancer patients

Cimetidine, a H(2) receptor antagonist, has been reported to improve survival in gastrointestinal cancer patients. These effects have largely been attributed to the enhancing effects of cimetidine on the host's antitumour cell-mediated immune response, such as inhibition of suppressor T lymphocyte activity, stimulation of natural killer cell activity and increase of interleukin-2 production from helper T lymphocytes. We conducted an in vitro study on the effects of cimetidine on differentiation and antigen presenting capacity of monocyte-derived dendritic cells from advanced colorectal cancer patients and normal controls. As a result, an investigation of expression of surface molecules associated with dendritic cells by flow cytometric analyses showed that cimetidine had no enhancing effect on differentiation of dendritic cells from cancer patients and normal controls. An investigation of [(3)H]thymidine incorporation by allogeneic mixed lymphocyte reactions revealed that cimetidine increased the antigen presenting capacity of dendritic cells from both materials. Moreover, a higher antigen presenting capacity was observed in advanced cancer patients compared to normal controls. These effects might be mediated via specific action of cimetidine and not via H(2) receptors because famotidine did not show similar effects. Our results suggest that cimetidine may enhance the host's antitumour cell-mediated immunity by improving the suppressed dendritic cells function of advanced cancer patients.