Pharmacology and toxicology of nizatidine

Effects of ranitidine and nizatidine on the risk of gastrointestinal cancer

Purpose

Gastrointestinal (GI) cancer occurs in digestive organs such as the stomach, colon, liver, esophagus, and pancreas. About 83,034 cases occurred in Korea alone in 2020. Dietary factors, alcohol consumption, Helicobacter pylori (H. pylori), and lifestyle factors increase the incidence of diseases such as gastritis, peptic ulcer, pancreatitis, and gastroesophageal reflux disease (GERD), which can develop into GI cancer. However, in 2019, the US Food and Drug Administration announced that the drugs ranitidine and nizatidine, which are used for digestive disorders, contain carcinogens. In this study, we investigated the effects of ranitidine and nizatidine on the development of GI cancer.

Materials and methods

In this study, using National Health Insurance Service-National Sample Cohort (NHIS-NSC) version 2.5 (updated from 2002 to 2019), subjects who developed GI cancer were enrolled in the case group, and those who were at risk of, but did not develop, cancer were enrolled in the control group. Thereafter, risk-set matching was performed (1:3 ratio) by sex and age at the time of diagnosis of cancer in the case group. Through this procedure, 22,931 cases and 68,793 controls were identified. The associations of ranitidine and/or nizatidine with GI cancer were confirmed by adjusted odds ratios (aORs) and 95% confidence intervals (CIs) calculated through conditional logistic regression analysis.

Results

The aORs of ranitidine and/or nizatidine users were lower than those of nonusers in all average prescription days groups (< 30 days/year: aOR [95% CI] = 0.79 [0.75-0.82]; 30-59 days/year: aOR [95% CI] = 0.66 [0.59-0.73]; 60-89 days/year: aOR [95% CI] = 0.69 [0.59-0.81]; ≥ 90 days/year: aOR [95% CI] = 0.69 [0.59-0.79]). Sensitivity analyses were conducted with different lag periods for the onset of GI cancer after drug administration, and these analyses yielded consistent results. Additional analyses were also performed by dividing subjects into groups based on cancer types and CCI scores, and these analyses produced the same results.

Conclusion

Our study, using nationwide retrospective cohort data, did not find evidence suggesting that ranitidine and nizatidine increase the risk of GI cancer. In fact, we observed that the incidence of GI cancer was lower in individuals who used the drugs compared to nonusers. These findings suggest a potential beneficial effect of these drugs on cancer risk, likely attributed to their ability to improve digestive function.

The Physiology of the Gastric Parietal Cell

Parietal cells are responsible for gastric acid secretion, which aids in the digestion of food, absorption of minerals, and control of harmful bacteria. However, a fine balance of activators and inhibitors of parietal cell-mediated acid secretion is required to ensure proper digestion of food, while preventing damage to the gastric and duodenal mucosa. As a result, parietal cell secretion is highly regulated through numerous mechanisms including the vagus nerve, gastrin, histamine, ghrelin, somatostatin, glucagon-like peptide 1, and other agonists and antagonists. The tight regulation of parietal cells ensures the proper secretion of HCl. The H+-K+-ATPase enzyme expressed in parietal cells regulates the exchange of cytoplasmic H+ for extracellular K+. The H+ secreted into the gastric lumen by the H+-K+-ATPase combines with luminal Cl- to form gastric acid, HCl. Inhibition of the H+-K+-ATPase is the most efficacious method of preventing harmful gastric acid secretion. Proton pump inhibitors and potassium competitive acid blockers are widely used therapeutically to inhibit acid secretion. Stimulated delivery of the H+-K+-ATPase to the parietal cell apical surface requires the fusion of intracellular tubulovesicles with the overlying secretory canaliculus, a process that represents the most prominent example of apical membrane recycling. In addition to their unique ability to secrete gastric acid, parietal cells also play an important role in gastric mucosal homeostasis through the secretion of multiple growth factor molecules. The gastric parietal cell therefore plays multiple roles in gastric secretion and protection as well as coordination of physiological repair.

Estimation of nizatidine gastric nitrosatability and product toxicity via an integrated approach combining HILIC, in silico toxicology, and molecular docking

The liability of the H₂-receptor antagonist nizatidine (NZ) to nitrosation in simulated gastric juice (SGJ) and under WHO-suggested conditions was investigated for the first time. For monitoring the nitrosatability of NZ, a hydrophilic interaction liquid chromatography (HILIC) method was optimized and validated according to FDA guidance. A Cosmosil HILIC® column and a mobile phase composed of acetonitrile: 0.04 M acetate buffer pH 6.0 (92:8, v/v) were used for the separation of NZ and its N-nitroso derivative (NZ-NO) within 6 min with LODs of 0.02 and 0.1 μg/mL, respectively. NZ was found highly susceptible to nitrosation in SGJ reaching 100% nitrosation in 10 min, while only 18% nitrosation was observed after 160 min under the WHO-suggested conditions. The chemical structure of NZ-NO was clarified by ESI⁺/MS. In silico toxicology study confirmed the mutagenicity and toxicity of NZ-NO. Experiments evidenced that ascorbic acid strongly suppresses the nitrosation of NZ suggesting their co-administration for protection from potential risks. In addition, the impacts of the HILIC method on safety, health, and environment were favorably evaluated by three green analytical chemistry metrics and it was proved that, unlike the popular impression, HILIC methods could be green to the environment.

Gastroesophageal reflux disease in pregnancy

Gastroesophageal reflux disease during pregnancy is common. Altered structure and function of the normal physiological barriers to reflux of gastric contents into the oesophagus explain the high incidence of this problem in pregnant women. For the majority of patients, life-style modifications are helpful, but are not sufficient to control symptoms and medication is required. The optimum management of reflux in pregnant patients requires special attention and expertise, since the safety of the mother, foetus and neonate remain the primary focus. Gastroenterologists and obstetricians should work together to optimise treatment. Typically, one utilises a step-up program that starts with life-style modifications and antacids. If those methods fail, histamine-2 receptor antagonists and proton pump inhibitors are tried. Rarely, promotility agents are used. Initiation of these medications must be undertaken after a careful discussion of risks and benefits with patients. In patients without a prior history of reflux, symptoms usually abate after delivery.

Gastrointestinal medications in pregnancy

Management of the pregnant patient presents unique challenges to the treating physician. Current Food and Drug Administration classifications do not necessarily reflect clinical experience or recent literature. Ideally, one should use the lowest-risk drug possible, with attention to the appropriate level of efficacy for the patient's condition, the stage of pregnancy and dose adjustment. Every treatment decision should be fully discussed with the patient and a multidisciplinary team that should include the obstetrician and, if appropriate, the paediatrician. This review will cover the medications commonly used to treat gastrointestinal disease. The majority of medications can be categorised as 'low risk' or 'should be avoided'. The following medications should never be used during pregnancy due to the clear risk of teratogenicity or adverse events: bismuth, castor oil, sodium bicarbonate, methotrexate, ribavirin, doxycycline, tetracycline, and thalidomide.

American gastroenterological association institute technical review on the use of gastrointestinal medications in pregnancy

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Institute Clinical Practice and Economics Committee. The paper was approved by the Committee on February 22, 2006 and by the AGA Institute Governing Board on April 20, 2006.

Review article: the management of heartburn in pregnancy

Heartburn is a normal consequence of pregnancy. The predominant aetiology is a decrease in lower oesophageal sphincter pressure caused by female sex hormones, especially progesterone. Serious reflux complications during pregnancy are rare; hence upper endoscopy and other diagnostic tests are infrequently needed. Gastro-oesophageal reflux disease during pregnancy should be managed with a step-up algorithm beginning with lifestyle modifications and dietary changes. Antacids or sucralfate are considered the first-line drug therapy. If symptoms persist, any of the histamine2-receptor antagonists can be used. Proton pump inhibitors are reserved for women with intractable symptoms or complicated reflux disease. All but omeprazole are FDA category B drugs during pregnancy. Most drugs are excreted in breast milk. Of systemic agents, only the histamine2-receptor antagonists, with the exception of nizatidine, are safe to use during lactation.

Gastroesophageal reflux disease during pregnancy

Approximately two thirds of pregnant patients develop heartburn. The origin is multifactorial, but the predominant factor is a decrease in LES pressure caused by female sex hormones, especially progesterone. Mechanical factors play a small role. Serious reflux complications during pregnancy are rare; therefore EGD and other diagnostic tests are infrequently needed. Symptomatic GERD during pregnancy should be managed with a step-up algorithm beginning with lifestyle modifications and dietary changes. Antacids or sucralfate are considered the first-line medical therapy. If symptoms persist, H2RAs should be used. Ranitidine is probably preferred because of its documented efficacy and safety profile in pregnancy, even in the first trimester. Proton-pump inhibitors are reserved for the woman with intractable symptoms or complicated reflux disease. Lansoprazole may be the preferred PPI because of its safety profile in animals and case reports of safety in human pregnancies.

Gastric and duodenal ulcers during pregnancy

The frequency, symptoms, and complication rate of PUD seem to decrease during pregnancy. Yet clinicians often have to treat dyspepsia or pyrosis of undetermined origin during pregnancy because the frequency of pyrosis significantly increases during pregnancy, and clinicians reluctantly perform EGD during pregnancy for pyrosis to differentiate reliably between GERD and PUD. Dyspepsia or pyrosis during pregnancy is initially treated with dietary and lifestyle modifications. If the symptoms do not remit with these modifications, sucralfate or antacids, preferably magnesium-containing or aluminum-containing antacids, should be administered. Histamine2 receptor antagonists are recommended when symptoms are refractory to antacid or sucralfate therapy. Ranitidine seems to be a relatively safe H2 receptor antagonist. If symptoms continue despite H2 receptor antagonist therapy, the patient should be evaluated for possible EGD or PPI therapy. Pregnant women with hemodynamically significant upper gastrointestinal bleeding or other worrisome clinical findings should undergo EGD. Indications for surgery include ulcer perforation, ongoing active bleeding from an ulcer requiring transfusion of six or more units of packed erythrocytes, gastric outlet obstruction refractory to intense medical therapy, and a malignant gastric ulcer without evident metastases.

Abdominal pain during pregnancy

Numerous medical, surgical, psychiatric, gynecologic, and obstetric disorders can cause abdominal pain during pregnancy. The patient history, physical examination, laboratory data, and radiologic findings usually provide the diagnosis. The pregnant woman has physiologic alterations that affect the clinical presentation, including atypical normative laboratory values. Abdominal ultrasound is generally the recommended radiologic imaging modality; roentgenograms are generally contraindicated during pregnancy because of radiation teratogenicity. Concerns about the fetus limit the pharmacotherapy. Maternal and fetal survival have recently increased in many life-threatening conditions, such as ectopic pregnancy, appendicitis, and eclampsia, because of improved diagnostic technology, better maternal and fetal monitoring, improved laparoscopic technology, and earlier therapy.

Evaluation of rat intestinal absorption data and correlation with human intestinal absorption

The absorption of 111 drug and drug-like compounds was evaluated from 111 references based on the ratio of urinary excretion of drugs following oral and intravenous administration to intact rats and biliary excretion of bile duct-cannulated rats. Ninety-eight drug compounds for which both human and rat absorption data were available were selected for correlation analysis between the human and rat absorption. The result shows that the extent of absorption in these two species is similar. For 94% of the drugs the absorption difference between humans and rats is less than 20% and for 98% of drugs the difference is less than 30%. There is only one drug for which human absorption is significantly different from rat absorption. The standard deviation is 11% between human and rat absorption. The linear relationship between human and rat absorption forced through the origin, as determined by least squares regression, is %Absorption (human)=0.997%Absorption (rat) (n=98, SD=11). It is suggested that the absorption in rats could be used as an alternative method to human absorption in pre-clinical oral absorption studies.

Treating gastro-oesophageal reflux disease during pregnancy and lactation: what are the safest therapy options?

Gastro-oesophageal reflux and heartburn are reported by 45 to 85% of women during pregnancy. Typically, the heartburn of pregnancy is new onset and is precipitated by the hormonal effects of estrogen and progesterone on lower oesophageal sphincter function. In mild cases, the patient should be reassured that reflux is commonly encountered during a normal pregnancy: lifestyle and dietary modifications may be all that are required. In a pregnant woman with moderate to severe reflux symptoms, the physician must discuss with the patient the benefits versus the risks of using drug therapy. Medications used for treating gastro-oesophageal reflux are not routinely or vigorously tested in randomised, controlled trials in women who are pregnant because of ethical and medico-legal concerns. Safety data are based on animal studies, human case reports and cohort studies as offered by physicians, pharmaceutical companies and regulatory authorities. If drug therapy is required, first-line therapy should consist of nonsystemically absorbed medications, including antacids or sucralfate, which offer little, if any, risk to the fetus. Systemic therapy with histamine H2 receptor antagonists (avoiding nizatidine) or prokinetic drugs (metoclopramide, cisapride) should be reserved for patients with more severe symptoms. Proton pump inhibitors are not recommended during pregnancy except for severe intractable cases of gastrooesophageal reflux or possibly prior to anaesthesia during labour and delivery. In these rare situations, animal teratogenicity studies suggests that lansoprazole may be the best choice. Use of the least possible amount of systemic drug needed to ameliorate the patient's symptoms is clearly the best for therapy. If reflux symptoms are intractable or atypical, endoscopy can safely be performed with conscious sedation and careful monitoring the mother and fetus.

Treatment of childhood peptic esophagitis: a double-blind placebo-controlled trial of nizatidine

BACKGROUND

Nizatidine is an H2 histaminic receptor blocker, which acts on the oxintic cells in the stomach. The efficacy of nizatidine on acid gastric secretion has been widely studied in adults with erosive and ulcerative esophagitis, but not in children. The aim of the present study was to evaluate the therapeutic efficacy of nizatidine in children with reflux esophagitis.

METHODS

Twenty-six patients were studied; all of them underwent endoscopy with multiple esophageal biopsies and 24-h intraesophageal pH monitoring. The diagnosis of esophagitis was based on histologic features. Patients were randomly assigned to double-blind treatment with either nizatidine or a placebo (10 mg/kg/day in two doses) for 8 weeks. A symptomatic score assessment was evaluated during the study.

RESULTS

Twenty-four patients completed the 8-week protocol. After therapy, 9/13 (69%) patients on nizatidine and 2/13 (15%) patients on the placebo were healed (p < 0.007 by Fisher's exact test). Histological findings were improved in two other (16.7%) patients and unchanged in the last (8.3%) patient on nizatidine. In the placebo group there was histological improvement in three (25%) patients, no variation in six (50%), and worsening in one (8.3%). After therapy, determination of esophageal pH showed a statistically significant decrease of the total acid exposure time (p < 0.01) only in the nizatidine group. The clinical score analysis showed an improvement of symptoms only in the nizatidine group (p < 0.01), except for vomiting, which was reduced in both groups.

CONCLUSIONS

Our results show that nizatidine is effective in treating children with reflux esophagitis. The children included in this study did not have severe esophagitis, and the conclusion must be limited to those with mild to moderate degrees of disease.

Nizatidine accelerates gastric emptying of a solid meal in rats

Nizatidine, a new histamine-2-receptor antagonist, stimulates gastrointestinal motility in dogs and gastric emptying of liquids in rats. Effect of nizatidine on gastric emptying of a solid meal was investigated using a novel gastric emptying model in rats. Male Wistar rats (weighing 200-300 g) were supplied with powdered food containing 30 w/w% barium 14 hr before the beginning of the experiment and x-ray photography of rat stomach was taken under light ether anesthesia. Gastric emptying was assessed by percentage of a decrease in area 30 min after drug was injected intraperitoneally. There was a positive correlation between the area of the gastric outline and the weight of the gastric contents (r = 0.94, P < 0.01). Ether anesthesia itself did not affect gastric emptying. Nizatidine increased gastric emptying dose-dependently (emptied percentage; vehicle: 4.9 +/- 1.5%, 1 mg/kg: 7.2 +/- 0.4%, 3 mg/kg: 10.4 +/- 2.0%, 10 mg/kg: 16.7 +/- 4.9%, 30 mg/kg: 25.7 +/- 7.4%). N-Desmethyl nizatidine (NDM) also stimulated gastric emptying, but nizatidine S-oxide, cimetidine, an famotidine had no significant effects on gastric emptying. Nizatidine and neostigmine, but not NDM, at a subthreshold dose accelerated gastric emptying treated with a low dose of acetylcholine (0.1 mg/kg). Atropine (2 mg/kg, -30 min) did not modulate the gastroprokinetic action of nizatidine, but blocked that of NDM. These findings suggest that this noninvasive method may allow measurement of gastric emptying of solids accurately and that nizatidine and NDM facilitate gastric emptying probably mediated by a direct and/or an indirect (acetylcholinesterase inhibition) cholinergic mechanism.

Changes in the effects of nizatidine and famotidine on cardiac performance after pretreatment with ranitidine

This was an open, randomized study of the cardiovascular effects of the histamine H2 receptor antagonists ranitidine, famotidine, and nizatidine after single oral doses alone or in combination in healthy volunteers. When compared with placebo ranitidine (450 mg) did not have any haemodynamic effects. Nizatidine (300 mg) caused significant falls in heart rate and cardiac output. Famotidine (40 mg) caused significant falls in stroke volume and cardiac output and an increase in pre-ejection period. Pretreatment with ranitidine abolished the haemodynamic effects of nizatidine and caused a time-shift of 2 h in the onset of the cardiovascular effects of famotidine. The difference in the results for nizatidine and famotidine can be explained by the longer half-life of famotidine. Vascular effects are assumed to be responsible for impairment of cardiac performance by famotidine.

Dose-dependent heart rate reducing effect of nizatidine, a histamine H2-receptor antagonist

1. Twelve healthy subjects were treated in a randomised placebo-controlled crossover study with placebo, 150 mg, 300 mg, and 600 mg nizatidine, 100 mg pirenzepine, and 300 mg nizatidine plus 100 mg pirenzepine for 1 week each. 2. On the seventh treatment day, heart rate, blood pressure, systolic time intervals, impedance cardiographic and Doppler ultrasound variables were measured. 3. Stroke volume and blood pressure were not altered by nizatidine and/or pirenzepine. By contrast, heart rate and cardiac output significantly (P < 0.05) decreased in a dose-dependent manner 1.5 and 3 h after administration of 300 and 600 mg nizatidine. Treatment with 150 mg nizatidine led to similar though non-significant trends. 4. While a slightly insignificant rise in heart rate was detected with pirenzepine alone, heart rate and cardiac output remained unchanged upon combined nizatidine and pirenzepine treatment as compared with placebo and baseline values. 5. In conclusion, nizatidine reduced heart rate and cardiac output in a dose-dependent manner, whereas this negative chronotropic effect was counteracted by concurrent administration of the anti-cholinergic drug pirenzepine.

Hemofiltrability of histamine H2-receptor antagonist, nizatidine, and its metabolites in patients with renal failure

To study if an H2-receptor antagonist, nizatidine, and its metabolites [N-2-monodesmethylnizatidine (N-2-MDMN) and nizatidine sulfoxide (nizatidine S-Ox)] would be removed by an arteriovenous hemofiltration, the authors measured their plasma concentrations and amounts recovered in ultrafiltrate during 11 sessions of an intermittent hemofiltration performed in seven patients with renal failure who were given an oral administration of nizatidine (150 mg). The concentrations of the parent drug and its metabolites in plasma and ultrafiltrate were determined with a high-performance liquid chromatography with ultraviolet absorbance detection. The mean (+/- standard deviation [SD]) amounts of nizatidine removed by the procedure performed at the mean ultrafiltration rate of 18 (range, 11-25) mL/min over the mean duration of 179 (60 to 300) minutes accounted for 1.9 +/- 1.4% of the dose administered. The corresponding values for N-2-MDMN and nizatidine S-Ox were 0.3 +/- 0.2% and 0.2 +/- 0.2% of the molar dose of nizatidine, respectively. There was a significant correlation between the filtration rate and the hemofiltration clearance of nizatidine (r = .94, P < .001) or its active metabolite, N-2-MDMN (r = 0.83, P < .01), indicating that the sieving coefficient (Sc), an index of filtration efficiency, for these compounds is largely constant (0.59 and 0.67 for nizatidine and N-2-MDMN, respectively) under the current hemofiltration conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of a single oral morning dose of nizatidine and ranitidine on intragastric pH under basal conditions and after pentagastrin stimulation

A comparison was made of the antisecretory activity of orally administered nizatidine and ranitidine by measuring intragastric pH under basal conditions and during and after pentagastrin stimulation. Intragastric pH values were measured with a bipolar glass electrode in 10 patients with healed duodenal ulcers treated with nizatidine or ranitidine according to a randomized single-blind design. The antisecretory activity of the two drugs was similar during the 4 h of monitoring following drug administration. Nizatidine, however, showed a more rapid inhibitory action than ranitidine, producing a significantly greater increase in pH with respect to basal values during pentagastrin infusion. In the period following infusion the pH values observed with ranitidine were higher than with nizatidine, but not significantly so. Under these experimental conditions, therefore, the antisecretory activity of nizatidine was shown to be more rapid than that of ranitidine and equally effective.

Pharmacokinetics of nizatidine in dogs and rats

1. Plasma levels of nizatidine and two metabolites (N-desmethyl nizatidine and nizatidine S-oxide) were studied in dogs and rats. 2. The time-courses of plasma concentration of nizatidine after i.v. and oral administration to dogs well fitted a two-compartment model. Absorption after oral administration was rapid, and the peak plasma level (Cmax) and area under the plasma concentration-time curve (AUC) were proportional to doses. Absolute bioavailability was close to 100%, indicating that nizatidine has a negligible first-pass effect. 3. Nizatidine was eliminated by apparent first-order kinetics after i.v. administration to rats, and the elimination in rats was faster than in dogs. Bioavailability in rats was 72.4%, indicating a slight first-pass effect in rats. 4. When plasma clearance (Clp), or volume of distribution (Vd.beta), of nizatidine were plotted against animal body weight on a log-log scale, good correlations were obtained for rats, dogs and humans. 5. Peak levels (Cmax) of two metabolites were reached at 0.5-1.0 h after oral and i.v. administration of nizatidine to dogs. The elimination curves of the two metabolites were similar to that of nizatidine. Significant relationships were found between doses of nizatidine and Cmax or AUC of both metabolites.

Low bedtime doses of H2-receptor antagonists for acute treatment of duodenal ulcer

Twenty-four-hour intragastric acidity was measured continuously over five separate occasions in 15 patients with healed duodenal ulcers. They were randomized to receive either placebo, cimetidine 800 mg, ranitidine 150 mg, famotidine 20 mg, or nizatidine 150 mg, given at 2200 hr in double-blind fashion. All H2-receptor blockers were more effective than placebo in suppressing both circadian (P less than 0.05-P less than 0.01) and nocturnal (P less than 0.002) gastric acidity, while there was no significant differences between the effects of the four active drugs in the same time periods. The percentage of nocturnal acid inhibition (2300-0800 hr) over placebo in terms of H+ values was virtually 100% with all active treatments. The effect on daytime (0800-1700 hr) and evening (1700-2300 hr) acidity of both placebo and the four H2-receptor antagonists was similar. Therefore, in the above doses H2-receptor blockers guarantee overnight anacidity to a similar degree and cause the physiological buffering of daily meals on gastric acidity to be fully exploited. Furthermore, the reducing effect of daily meals on drug action can be prevented. Since strong acid suppression strictly confined to the nocturnal period has been shown to be closely correlated with the highest ulcer healing rates, it is suggested that single low bedtime doses of H2-receptor antagonist should be evaluated in the acute treatment of duodenal ulcer.

Rebound nocturnal hypersecretion after four weeks treatment with an H2 receptor antagonist

Daytime intragastric pH, fasting and meal stimulated serum gastrin and nocturnal acid output were studied in eight male duodenal ulcer patients before, during and two days after completing nizatidine 300 mg nocte (20:00 h) for four weeks. Median nocturnal acid output (mmol/10 h) decreased during treatment to 11.6 (range 0.4-26.7) compared with pretreatment value of 39.4 (9.8-91.2); median acid inhibition 77% (p less than 0.01) which was strongest between 24:00 and 04:00 h. Two days after discontinuing treatment, nocturnal acid output increased to 74.1 (11-181). Compared with the pretreatment value this represents median rebound hypersecretion of 77% (p less than 0.05), caused by increased H+ concentration and volume of secretion. Overall median daytime intragastric pH (09:00-21:00 h) was unchanged on the final day of treatment and two days after completing therapy, compared with the pretreatment values. Fasting serum gastrin measured between 09:30 and 10:00 h and the integrated gastrin response to an OXO breakfast taken out at 10:00 h were also similar during and after treatment, compared with pretreatment values. The rebound nocturnal hypersecretion may be relevant to the high ulcer relapse rates after stopping H2 receptor antagonists.

Nizatidine. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and its therapeutic use in peptic ulcer disease

Nizatidine is an H2-receptor antagonist which in animal studies was more active on a weight-for-weight basis than cimetidine in inhibiting basal and stimulated gastric acid secretion. Similarly, studies in humans have confirmed that nizatidine is a potent inhibitor of basal, nocturnal and stimulated gastric acid secretion. As might be expected at this stage of its development, published therapeutic experience with nizatidine is limited. Nevertheless, multicentre therapeutic trials have shown that nizatidine 300mg at bedtime or 150mg twice daily is significantly more effective than placebo for healing active duodenal ulcer, and is apparently as effective as standard doses of ranitidine in increasing the rate of healing of both duodenal and gastric ulcers, and as effective as a standard dose of cimetidine in active duodenal ulcer. When used prophylactically a single 150mg dose of nizatidine at night produces a decrease in the incidence of ulcer recurrence compared with placebo, and a similar rate of decrease to that achieved with ranitidine 150mg. Nizatidine is well tolerated. Unlike cimetidine it does not have any antiandrogenic effects or alter the hepatic metabolism of drugs. However, only wider clinical experience with nizatidine can accurately determine its relative efficacy and tolerability compared with other antiulcer therapy. Thus, early clinical experience suggests that nizatidine is a useful alternative to the histamine H2-receptor antagonists presently in clinical use.

Twenty four hour intragastric acidity and plasma gastrin concentration in healthy volunteers taking nizatidine 150 mg, nizatidine 300 mg, ranitidine 300 mg, or placebo at 21:00 h

Nine healthy volunteers were studied on the seventh day of dosing at 21:00 h with nizatidine 150 mg (N 150), nizatidine 300 mg (N 300), ranitidine 300 mg (R 300), or placebo, given in a predetermined random order. The double-blind 24 hour studies, using the Royal Free Hospital standard protocol, simultaneously measured intragastric acidity and plasma gastrin concentration. Compared with placebo, subjects responded to dosing with each H2-antagonist by a significant decrease of 24 hour intragastric acidity (N 150-45%; N 300-49% R 300-56%; p less than 0.01) and a significant rise of plasma gastrin concentration (N 150 + 20%; N 300 + 27%; R 300 + 58%; p less than 0.01). All three drug regimens caused similar significant decreases of nocturnal acidity (N 150-72%; N 300-79%; R 300-85%; p less than 0.01) and increases of nocturnal plasma gastrin concentration (N 150 + 41%; N300 + 52%; R 300 + 80%; p less than 0.01). Dosing with ranitidine 300 mg at 21:00 h also caused a simultaneous significant decrease of morning acidity (-32%; p less than 0.05) with a significant increase of plasma gastrin concentration (+36%; p less than 0.05), but the antisecretory effects of nizatidine 150 or 300 mg at 21:00 h were only observed during the night, with no effect during the morning. No drug regimen had any effect on acidity or plasma gastrin in the afternoon or early evening.

Histamine H2-receptor antagonists

The first histamine H2-receptor antagonists were developed in the early 1970s, and they have a dominant role in today's management of peptic ulceration. The original regimens using either cimetidine or ranitidine attempted to control acidity across the 24 hours, but more 'modern' regimens use a large single dose of the H2-blocker in the evening, which produces a pulse of decreased intragastric acidity during the night with a normal acidity in the daytime. High-dose regimens using a new generation of extremely potent histamine H2-receptor antagonists may improve ulcer healing rates at 4 weeks, and may be particularly useful for the management of either severe oesophagitis or intractable duodenal ulceration.

Do nizatidine and cimetidine interact with ibuprofen?

The potential for interaction between ibuprofen and two histamine H2-receptor blocking drugs--nizatidine and cimetidine--was investigated in six healthy male volunteers aged 20 to 25 years. Each subject received placebo, nizatidine 300 mg and cimetidine 800 mg orally at 9.00 p.m. daily for six doses in three randomised treatment periods separated by eight days. On the third day of each treatment period ibuprofen 400 mg was administered at the same time and venous blood samples were taken at intervals throughout the night and subsequently up to 84 h after administration. There was no difference in the area under the plasma concentration-time curve, rate of absorption or half-life of elimination of ibuprofen between the three treatments. The elimination half-life of ibuprofen on placebo was 2.04 h. The elimination half-life of nizatidine on ibuprofen was 1.72 h and that of cimetidine was 3.54 h. The latter is higher than previously reported in normal subjects. It is concluded that neither H2-blocker affects the kinetics of ibuprofen in man.