Safety of nizatidine in clinical trials conducted in the USA and Europe

Safety profile of long-term H2-antagonist therapy

The safety profile of low-dose maintenance therapy with H2-antagonists for duodenal ulcer disease suggests that these agents can be given safely for several years and probably much longer. Because information regarding the use of these compounds for more than 10 years in large numbers of patients is lacking, the safety of these drugs should continue to be monitored. The safety profiles of famotidine and nizatidine will require several additional years of postmarking surveillance data to match the depth of our knowledge regarding cimetidine and ranitidine. Compared to a surgical approach to ulcer disease, continuous H2-blocker maintenance therapy is cost-effective and is associated with significantly less morbidity. Patients with a history of bleeding or other ulcer complication should be encouraged to remain on maintenance therapy if they do not undergo surgery. The need for extended maintenance therapy also applied to individuals with frequent symptomatic ulcer relapses, reflux oesophagitis, and a range of less common disorders. Currently, H2-blockers and sucralfate are the only agents approved by the Food and Drug Administration for maintenance therapy of duodenal ulcer disease. Experience with omeprazole is still limited, and its long-term safety profile must await the completion of controlled trials of maintenance therapy. Given the apparent long-term safety of the H2-blockers for maintenance therapy, any new agent must prove to be equally safe in the clinical arena, a task that may be indeed formidable.

Effect of preoperative oral use of erythromycin and nizatidine on gastric pH and volume

This randomized controlled trial examined the effects of preoperative oral erythromycin or nizatidine on gastric pH and volume. Sixty patients, ASA 1 and 2 status scheduled for elective surgery were studied. All subjects received oral study medication with 10 ml of water 60 minutes prior to surgery. Patients in Group 1 (n=20) were given erythromycin 200 mg, in Group 2 (n=20) nizatidine 300 mg, and in Group 3 (n=20) placebo capsule. A nasogastric tube was inserted immediately after anaesthesia induction. Gastric content was aspirated, and volume and pH recorded. pH values determined in Group 1 were 5.6+/-1.87; in Group 2, 5.65+/-1.92 and in Group 3, 3.5+/-1.93. There was no statistical difference between Groups 1 and 2, but there was a statistically significant difference between Group 3 and Groups 1 and 2 (P<0.001). The volume of gastric content was 10.25+/-6.65 ml in Group 1, 10.3+/-6.29 ml in Group 2 and 20.25+/-16.72 ml in Group 3. Again, there was no statistical difference between Groups 1 and 2, but there was a statistically significant difference between Group 3 and Groups 1 and 2 (P<0.05). The proportion of patients considered "at risk" of significant lung injury should aspiration occur was 10% of Group 1, 5% of Group 2 and 20% of Group 3 (not statistically different). We conclude that oral erythromycin and nizatidine given one hour prior to surgery are effective in reducing gastric pH and volume.

Safety of acid-suppressing drugs

There is an extensive literature on the adverse effects of drugs that inhibit gastric acid secretion. This study presents a critical examination of interactions between antisecretory drugs and other compounds, the frequency of serious adverse effects relating to various body systems, the safety of antisecretory drugs in pregnancy, and longer-term safety data from postmarketing surveillance studies. While interactions with some other drugs, alcohol, and certain carcinogens are of potential concern, in practice clinically significant reactions appear to be rare if they occur at all. A small number of major side-effects have been documented, but they occur rarely, and postmarketing surveillance has not detected other longer-term sequelae. Safety of these drugs in pregnancy is not established, as data are so few. It is concluded that antisecretory agents, by comparison with most other classes of drugs, are remarkably well tolerated.

Clinical and statistical issues in therapeutic equivalence trials

Absolute proof of efficacy can only be given by placebo controlled trials. It is, however, important to classify a drug within the spectrum of existing therapeutic alternatives and, where effective treatment is available, it may be imperative due to ethical considerations to demonstrate that one drug is as effective as another. The issue of therapeutic equivalence trials is discussed along the lines of the important items which should be defined in the protocol: a) the target parameter, which is the primary endpoint of the trial, b) the reference drug, which should be selected with respect to efficacy (superior to others), and safety (largest amount of data), c) the acceptance range, which depends on the primary endpoint, and its implication for the clinical endpoints of morbidity and mortality (the conventional acceptance range for bioequivalence trials does not apply), and d) the statistical procedures, which must take into consideration the unsuitability of the conventional power approach for confirming equivalence. In an equivalence trial, compared to those that are placebo-controlled, the proof that one drug is as effective as another relies much more upon the quality of conduct of the study according to Good Clinical Practice.

Practical pharmacology and cost-effective management of peptic ulcer disease

The clinical approach to the therapy of peptic ulcer disease has changed over the years as our understanding of its pathogenesis has grown. No longer is excess acid production seen as the single cause of ulcer disease; rather, its pathogenesis is viewed as the disturbance of a complex balance of ulcerogenic and protective factors. Today, the clinician's aim is to restore the balance between protective and aggressive factors. Simultaneously, the development of new classes of medications has provided the clinician with the tools to decrease intragastric acidity, neutralize or suppress acid production, and enhance the protective and restorative properties of the mucosa.

Nizatidine suppression of basal gastric acid output: a comparison of two intravenous dosage regimens

To study the pharmacokinetics and pharmacodynamics of two intravenous nizatidine dosing regimens, serial plasma concentrations and continuous intragastric pH were monitored simultaneously in 10 subjects with a documented history of duodenal or gastric ulcers. A 24-hour gastric pH profile was characterized for a 300 mg daily dose of nizatidine randomly administered both as 100 mg every 8 hours and 150 mg every 12 hours. No significant differences were observed in the mean pharmacokinetic parameters between the two dosing regimens. Pharmacodynamic parameters for the 100 mg every 8 hours versus the 150 mg every 12 hours regimen were not significantly different except for percent of time during the 24-hour study period that the pH was maintained greater than 4 (43.6 +/- 20.7 versus 34.7 +/- 18.3, P less than .05). A significant relationship was demonstrated for both regimens (P less than .05) between the percent time pH greater than 4 and area under the plasma curve for the 24 hour study period. The lack of a significant difference in nizatidine pharmacokinetics between the two dosage regimens suggests a pharmacodynamic cause for the greater cumulative pH effect of the every 8 hour regimen.

Haematological adverse effects of histamine H2-receptor antagonists

Histamine H2-receptor antagonists are widely used in the treatment of gastrointestinal diseases related to gastric acid hypersecretion. Cimetidine was introduced into medical practice in 1976 and ranitidine, famotidine and nizatidine in 1981, 1985 and 1987, respectively. Haematological adverse effects are relatively uncommon and most have been reported in cases of cimetidine administration. These adverse effects are reviewed under 4 main headings: (a) blood cytopenias and leucocytosis; (b) coagulation disorders related to drug interactions with oral anticoagulants; (c) reduction of dietary iron absorption; and (d) reduction of dietary cobalamin absorption. 85 reported cases of blood cytopenias attributed to these drugs are reviewed, of which 75 (88%) were associated with cimetidine therapy. In postmarketing surveillance studies, the incidence of cimetidine-associated blood cytopenia has been evaluated at about 2.3 per 100,000 patients. Neutropenia and agranulocytosis are by far the most frequently encountered. Whatever the drug or the type of cytopenia, this adverse effect is almost always rapidly reversible when treatment is stopped. Moreover, in several cases other factors such as underlying diseases or additional drugs could have been responsible, at least partly, for the cytopenia. The pathophysiological basis of these adverse effects remains poorly explained. Various mechanisms have been proposed, which in some cases are probably associated: (a) direct toxicity for haemopoietic stem cells; (b) drug-induced immune reactions leading to blood or bone marrow cell damage, and (c) drug interactions, with increased and prolonged action of potentially haematotoxic drugs. Mechanisms (a) and (c) appear to be of particular clinical importance in cases of impaired renal elimination of H2-receptor antagonists. Cimetidine and probably to a lesser extent ranitidine potentiate the action of oral anticoagulants of both coumarin and indanedione structure. This may result in haemorrhagic complications. Such action is a consequence of the reduced hepatic metabolism of oral anticoagulants through a dose-dependent, reversible inhibition of cytochrome P450. Malabsorption of dietary iron and cobalamin appears to result from inhibition of gastric secretion by the H2-receptor antagonists. This is of no clinical importance in short term treatment, but long term use of H2-receptor antagonists may theoretically contribute to the occurrence of iron or cobalamin deficiency anaemia.

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.

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.