Urinary excretion kinetics of famotidine in rats

Famotidine is a new histamine H2-receptor antagonist which has been demonstrated to be more potent than cimetidine and ranitidine in inhibiting gastric acid secretion. Nine groups of adult male Sprague-Dawley rats received an ia injection of various loading doses of famotidine followed immediately by a constant infusion of the drug at different rates for 6 hr. When steady state famotidine concentrations in plasma were low, renal clearance of the drug (CLR) was greater than glomerular filtration (GFR), and the ratio CLR/GFR was about 4.5 at plasma concentrations of 0.2-1.8 micrograms/ml, suggesting that famotidine was actively secreted by the renal tubules. The CLR decreased as famotidine concentration in plasma increased, and the ratio CLR/GFR approached 1 in the concentration range of 25-76 micrograms/ml, thus providing evidence for saturation of the secretory mechanism. The maximum rate of secretory transport (Tm) of famotidine averaged 180 micrograms/min/kg. On average, some 50-70% of an ia bolus dose was excreted in the urine as unchanged drug within 24 hr of administration. Over the dose range of 0.3-30 mg/kg famotidine, there was no dose-dependent effect on total or renal clearance. Since the lowest dose level, 0.3 mg/kg, is below the recommended human therapeutic dose for famotidine (0.6 mg/kg), the saturation of the renal excretion process observed here in rats is not likely to be of clinical significance.

Circadian monitoring of gastric juice mutagenicity

The circadian monitoring of intragastric pH and of the mutagenicity of 440 gastric juice samples collected hourly from 22 subjects provided evidence that, irrespective of diagnosis and treatment, a weak yet consistent increase in revertants can be detected in his- Salmonella typhimurium strains during the 3-4-h periods following each meal. The recorded mutagenic activity was not related to the histidine content of gastric juice, was due to thermostable components and was not significantly inhibited by administration of vitamin C. Various genetic mechanisms were involved, which were different from those consequent to the artificial supplementation of gastric juice with sodium nitrite. Treatment with a histamine H2-receptor antagonist (famotidine), either at dinner or at bedtime, was followed by a nocturnal plateau of mutagenicity. However, such effect was not due to mutagenicity of the drug or of its derivatives, but to the therapeutic rise in pH associated with its antisecretory activity.

Direct effects of H2-receptor antagonists on airway smooth muscle and on responses mediated by H1- and H2-receptors

Because it has been suggested that histamine H2-receptor antagonists may worsen airway constriction in asthmatic patients, we investigated the comparative effects of three histamine H2-receptor antagonists on guinea pig tracheal smooth muscle in vitro. When tested against resting tone, cimetidine, ranitidine and famotidine produced dose-related relaxation with pD2 values (negative log of ED50 for relaxation) (+/- SE, n; eq 5) of 3.20 +/- 0.04, 2.95 +/- 0.16 and 2.97 +/- 0.14, respectively. Concentrations that were below threshold for relaxation, did not elicit contraction. However, when the preparations were precontracted with histamine (10(-5)M), dose-response curves for relaxation were shifted to the right, and low-concentrations of all three histamine H2-antagonists augmented histamine-induced tone. When preparations were pretreated with cimetidine (10(-6) to 10(-4) M) and then tested for sensitivity to histamine, dose-response curves for histamine-induced contraction were shifted to the left (potentiated). These results provide further evidence for a modulatory effect of airway H2-receptors on the contractile response to histamine. In addition, since the concentrations associated with potentiation of histamine-induced contraction were about the same for all three H2-receptor antagonists (greater than or equal to 10(-5) M), our studies suggest a greater likelihood of airway constriction for the less potent H2-receptor antagonists that must be administered in higher clinical doses.

The antisecretory profile of action of the H2-receptor antagonists, famotidine, loxtidine, ranitidine and L-643,441 on the rat isolated gastric mucosa

Four H2-receptor antagonists, famotidine, loxtidine, ranitidine and L-643,441 were tested against gastric secretory concentration-response curves to histamine, methacholine and dibutyryl cyclic AMP (dbcAMP) on the rat isolated gastric mucosa. All four drugs inhibited the secretory response to histamine, but the nature of this H2-receptor antagonism differed according to the drug. Ranitidine and famotidine were competitive, fully surmountable antagonists of histamine, but loxtidine and L-643,441 were unsurmountable antagonists. At high concentrations, the H2-receptor antagonists caused a small inhibition of the secretory response to methacholine but had no effect on the secretory response to dbcAMP. The rat isolated gastric mucosa is a useful preparation for characterisation of the antisecretory effects of H2-receptor antagonists.

Clinical benefits of intravenously administered famotidine in the treatment of upper gastrointestinal hemorrhage caused by peptic ulcer and stress ulcer disease

Bleeding may stop spontaneously in mild or moderate cases of GI bleeding. Therefore, to prove that H2-receptor antagonists effectively stop GI bleeding, evaluation of the results of treatment in patients who are classified as severe cases by the Nagao taxonomy is needed. Data from the literature show that mortality is higher in patients with specific endoscopic findings, such as active bleeding, visible vessels, clot, or stain, than it is in patients without these findings. The criteria for establishing whether H2-receptor antagonists effectively control GI bleeding in severe cases include a reduction in mortality, in the rate of recurrent bleeding, or in the rate of emergency surgery. Data gathered from a current multicenter trial assessing the efficacy of 20 mg famotidine administered intravenously twice daily show that the rate of emergency surgery in patients with bleeding ulcer is 8.6%, which is substantially less than the 54.2% rate found in a retrospective review of patients treated before the introduction of H2-receptor antagonists. In addition, there were no deaths among famotidine-treated patients. Similarly, among patients with bleeding caused by stress ulcer, the percentage who were treated with famotidine and required emergency surgery was much less than that in the historical control group (15.8% versus 40.0%). Famotidine was effective in greater than or equal to 88% of patients with peptic ulcers and in 78.9% of patients with stress ulcers. Recurrent bleeding occurred more often in patients with exposed blood vessels. Intravenously administered famotidine is, therefore, effective for the control of GI bleeding caused by severe peptic ulcer and stress ulcer disease.

Reduction of gastric acidity with ranitidine or famotidine: early evening dosage is more effective than late evening dosage

The antisecretory effect of a once daily dose of ranitidine and famotidine was examined after administration of the drugs either immediately after dinner or 3 h after dinner. A placebo-controlled multiple cross-over study was performed in 7 healthy ambulatory volunteers. They were given, on 6 separate days at least 1 week apart, either placebo, ranitidine 300 mg or famotidine 40 mg, either immediately after dinner or 3 h later. Breakfast, lunch and dinner were standardized. 24-Hour intragastric acidity was measured with a combined glass electrode. Duration of secretory inhibition by a drug was defined as the nighttime period between the first rise of pH above and the final fall below 3.5. This value represents the 95% upper confidence limit of nighttime pH values during placebo treatment. Secretory inhibition with early and late administration of ranitidine lasted for 10.7 and 7.3 h, respectively (p = 0.012). With famotidine it lasted for 10.1 and 7.1 h, respectively (p = 0.005). Gastric acidity after dinner was decreased by early but not late intake of ranitidine and famotidine. Thus, both ranitidine and famotidine were more effective when taken early, immediately after dinner, than when taken late in the evening. This observation might affect the mode of ulcer treatment with these drugs.

Comparison of once-daily bedtime administration of famotidine and ranitidine in the short-term treatment of duodenal ulcer. A multicenter, double-blind, controlled study

A multicenter, double-blind, randomized, controlled study was conducted in 234 duodenal ulcer patients to compare the efficacy and safety of the H2-receptor antagonists famotidine and ranitidine in the treatment of duodenal ulcer. Patients received 40 mg famotidine (119 patients) or 300 mg ranitidine (115 patients) once daily at bedtime for 4 weeks. If ulcer lesions persisted, treatment was extended to 6 weeks. Efficacy was assessed by relief of symptoms and endoscopic findings of ulcer healing. Safety was determined on the basis of reports of side effects, results of laboratory tests, and, in selected patients, changes in plasma levels of hormones. The 4- and 6-week healing rates achieved with famotidine were 76% and 91%, respectively, and with ranitidine they were 76% and 87%, respectively; the differences in healing rates for the two drugs were not statistically significant. Similarly, both drugs provided satisfactory relief of pain and dyspeptic symptoms. However, famotidine produced significantly (P less than 0.05) greater relief of postprandial fullness and heartburn. The incidence of untoward effects was low in both treatment groups, and abnormal results in laboratory tests were observed in only one patient, a chronic alcoholic receiving famotidine, who withdrew from the study because of a slight elevation in serum transaminase levels. One patient in the ranitidine treatment group dropped out of the study because of a generalized urticarial rash; however, a causal relationship between drug and effect could not be established. The authors conclude that famotidine may be regarded as the best alternative to ranitidine in the treatment of duodenal ulcer.

Famotidine: postmarketing clinical experience

A postmarketing survey of famotidine usage (phase IV survey) tracked 6346 patients at 602 locations from August 1985 to April 1986. Through the survey, the efficacy and the safety of famotidine were studied. The patients included 4618 cases of peptic ulcer, 106 cases of reflux esophagitis, 1006 cases of upper gastrointestinal tract bleeding, 343 cases of bleeding and ulcer prophylaxis, and 273 cases of gastritis and other diseases, totalling 6346 patients. Efficacy was analyzed by type of disease in terms of overall improvement; results of intermittent hemostatic efficacy were obtained for upper gastrointestinal tract bleeding; and safety was assessed. Overall, the results were good; the 8-week healing rate was 92.4%, and 72.3% of patients had their bleeding controlled within 7 days of beginning famotidine therapy. Side effects occurred in only 0.43% of patients, and abnormalities in laboratory test results were observed in less than 1% of patients. Gastrointestinal side effects, especially constipation, occurred most frequently. Most side effects were mild. The results of this postmarketing survey indicate that famotidine is a safe and effective H2-receptor antagonist.

Continuous 24-hour intragastric pH monitoring in the evaluation of the effect of a nightly dose of famotidine, ranitidine and placebo on gastric acidity of patients with duodenal ulcer

In 11 duodenal ulcer patients, the antisecretory effects of bedtime famotidine 40 mg were compared to those obtained with ranitidine 300 mg and placebo by means of continuous 24-hour intragastric pH monitoring. The 24-hour areas under the curve of pH profiles of the two H2 blockers were significantly different from those related to placebo (p approximately 0 for ranitidine and p = 0.00001 for famotidine), but not from each other (p = 0.51). Onset and duration of the famotidine action, however, were respectively earlier and longer lasting (12 vs. about 9 h) than those of ranitidine. Famotidine was also significantly superior (p approximately 0) to ranitidine in keeping intragastric pH at high values (especially those comprised between 6 and 8 pH units), although theoretically equipotent doses of the two H2 antagonists were used.

Famotidine: proven once-a-day treatment for gastric ulcer

An 8-week, double-blind, randomized, placebo-controlled, multinational (n = 14), multicenter (n = 44) trial was conducted to determine whether famotidine speeds healing and relief of symptoms in patients with benign gastric ulcer. Of the 336 patients who entered the trial, 167 received 40 mg of famotidine in the evening, and 169 received placebo. At 4, 6, and 8 weeks after entry, ulcers had healed in a significantly (P less than 0.01) higher percentage of famotidine-treated patients than in those treated with placebo (47%, 65%, 80% versus 31%, 46%, 54%, respectively). Famotidine was also superior to placebo in relieving ulcer symptoms; the proportion of patients receiving additional antacid therapy was significantly lower in the famotidine group. The findings show that the new H2-receptor antagonist famotidine, administered as a single evening dose, significantly speeds the healing of benign gastric ulcers and that it is a safe and highly effective treatment of gastric ulceration. The convenient dosage regimen of famotidine (one tablet in the evening) should improve patient compliance, which, in turn, may result in faster healing of ulcers and a lower incidence of ulcer complications.

Famotidine and ranitidine: any difference in the duration of action?

The new H2-receptor antagonist famotidine was studied to test its duration of action in comparison with ranitidine. In the conscious cat provided with gastric fistula famotidine and ranitidine, administered by bolus i.v. injection, by continuous infusion or intragastrically, had an inhibitory effect on dimaprit-induced acid secretion which lasted similarly. The only difference between the two compounds was the higher potency of famotidine. Reversibility studies carried out in the isolated gastric fundus from immature rats showed that famotidine, like ranitidine, was easily washed out even at the highest concentration tested (3 X 10(-6) M) and thus it can be considered a readily dissociable H2 antagonist in this tissue.

Famotidine in the treatment of gastritis

H2-receptor antagonists are widely used in the treatment of diseases such as gastric and duodenal ulcers, hemorrhage of the upper digestive tract, and the Zollinger-Ellison syndrome. However, the usefulness of H2-receptor antagonists in treating erosions and/or mucosal hemorrhages has not been established. A multicenter, double-blind, comparative trial was conducted to determine the effects of famotidine, a new H2-receptor antagonist, for such lesions. Patients received one of three oral doses (5, 10, or 20 mg) of famotidine twice daily for 2 weeks. The comparative efficacy and safety of the three dosages of famotidine in the treatment of lesions were evaluated, using an assessment of subjective symptoms, endoscopic findings, and adverse reactions. Symptoms, including epigastric pain, heartburn, and discomfort, were relieved in a substantial number of patients as early as 3 days after beginning treatment with famotidine. Moreover, less than 30% of patients complained of these symptoms after 2 weeks of famotidine therapy. There were no significant differences among the three dosages in relief of symptoms. Endoscopic assessment for the presence of erosion and hemorrhage after 1 and 2 weeks of famotidine treatment showed that the 10- and 20-mg doses were more effective in healing erosions and hemorrhages than was the 5-mg dose. After 2 weeks of treatment, 88.5% and 91.7% of the patients in the 10- and 20-mg dosage groups, respectively, did not have evidence of erosions or hemorrhages, compared with 73% of patients in the 5-mg group.(ABSTRACT TRUNCATED AT 250 WORDS)

Once-daily administration of famotidine for reflux esophagitis

An open-labeled study of once-daily administration of 40 mg famotidine was conducted in 24 patients with endoscopically confirmed reflux esophagitis. The mean age of the patients was 62.8 years. Most had stage I or stage II esophagitis of 1 years' duration or less. After 4, 8, 12, and 16 weeks of treatment, endoscopically documented healing was reported in 50%, 75%, 82%, and 83% of patients, respectively. Among specific endoscopic findings documented at the start of the study there was clearing of white exudate in 83% of patients, and redness cleared in 50% of patients after 16 weeks of treatment. Symptomatic improvement was observed in 73% of patients after 2 weeks, and this increased to 81% and 85% after 4 and 8 weeks of treatment, respectively. Painful symptoms cleared within 2 weeks in 68% of patients, and this increased to 77% after 8 weeks of once-daily therapy. Famotidine was well tolerated. Historically, reflux esophagitis has not responded satisfactorily to drug treatment. The reported symptomatic response and the response documented by endoscopy after therapy with 40 mg famotidine once daily at bedtime are encouraging. Further studies should be conducted to define the role of famotidine in the treatment of reflux esophagitis.

Famotidine: a notable lack of drug interactions

Cimetidine, an H2-receptor antagonist, has been shown to inhibit the oxidative metabolism of several drugs by interacting with the hepatic cytochrome P450 system, which is involved in phase-I oxidative drug metabolism. Ranitidine, another H2-receptor antagonist, has been shown to have an extremely low level of interaction with the cytochrome P450 system. The potential of famotidine, a new H2-receptor antagonist with a guanylthiazole ring structure, to interact with the cytochrome P450 system has been extensively evaluated. Many of the studies used cimetidine and/or ranitidine as active controls. In vitro studies investigated the potential effects of famotidine coadministration on aminopyrine and diazepam demethylase activity, disturbances of P450 spectra, and effects on the metabolism of specific substrates such as deethylation of 7-ethoxycoumarin and demethylation of benzphetamine. Famotidine and ranitidine showed negligible interaction with the cytochrome P450 reactions studied, in contrast to the rather marked interaction demonstrated with cimetidine. Several in vivo animal studies investigated the effect of famotidine on hexobarbital sleeping time; plasma concentrations of diazepam, warfarin, and propranolol; antipyrine elimination kinetics; and warfarin prothrombin complex activity. Famotidine and ranitidine demonstrated either no evidence or minimal evidence of interaction with cytochrome P450 functions, in direct contrast to marked interactions produced by cimetidine. Human studies investigated the potential of an interaction with the coadministration of famotidine and aminopyrine, antipyrine, diazepam, theophylline, phenytoin, and warfarin. Coadministration of famotidine had no effect on the pharmacokinetic variables of theophylline, diazepam, desmethyldiazepam, and phenytoin and no effect on the half-life of antipyrine and aminopyrine or on the prothrombin time ratios associated with warfarin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

A multicenter, double-blind, randomized, placebo-controlled comparison of nocturnal and twice-a-day famotidine in the treatment of active duodenal ulcer disease

The efficacy and safety of famotidine, a potent new long-acting H2-receptor antagonist, was compared with placebo in a multicenter, double-blind, randomized, placebo-controlled study in the United States. A total of 384 patients with endoscopically proven acute duodenal ulcer disease were enrolled. Patients received either famotidine or a placebo. The patients receiving famotidine were treated with one of three dose regimens, 40 mg h.s., 40 mg b.i.d., or 20 mg b.i.d. Patients were reassessed by endoscopy at 2, 4, and 8 wk if ulcer healing had not occurred sooner. A diary was kept to record the duration and intensity of the day and night pain and the amount of Gelusil antacid (Parke-Davis, Morris Plains, N.J.) ingested. Three hundred sixty-three patients met the evaluation criteria. The results revealed a 4-wk healing rate of 70%, 75%, 67%, and 31% for the famotidine 40 mg h.s., 40 mg b.i.d., 20 mg b.i.d., and placebo groups, respectively. The 8-wk healing rates for the same respective groups were 83%, 82%, 82%, 45%. Ulcer pain and antacid consumption occurred less often in the famotidine groups. The clinical and laboratory safety profile of the famotidine groups was similar to that of the placebo group. Famotidine appears to be an effective and safe once-a-day therapy for the treatment of acute duodenal ulcer disease. The recommended dosage is 40 mg h.s.

Effect of five structurally diverse H2-receptor antagonists on drug metabolism

Some H2-receptor antagonists can interact with the biotransformation of other drugs. This is due to their binding to cytochrome P-450. We tested the in vitro effects of 5 different H2-receptor antagonists cimetidine (C), oxmetidine (O), ranitidine (R), famotidine (F) and nizatidine (N) on arylhydrocarbon-hydroxylase, 7-ethoxycoumarin-O-deethylase and 7-ethoxy-resorufin-O-deethylase activity using liver microsomes from man as well as from untreated, phenobarbital and 3-methylcholanthrene treated rats. In addition their binding to human microsomal cytochrome P-450 was evaluated. The in vivo effects of these antagonists were investigated on the hepatic elimination of diazepam in healthy volunteers. In vitro O was found to be the most effective inhibitor of the enzyme activities studied. C showed a clear inhibitory effect only with rat liver microsomes whereas the remaining drugs were more than 10 times less potent. The binding affinities of these antagonists showed a similar tendency: the Ks-values for O, C and R were 0.2, 0.9 and 5.1 mM, respectively; for F and N no binding up to 4 mM could be observed. However, in man, only C inhibited the hepatic elimination of diazepam by about 45% while R, O, N and F did not affect the pharmacokinetics of diazepam. Thus, it could be concluded from our studies that one cannot extrapolate in vitro data of the inhibitory potency of H2-receptor antagonists in every case to human in vivo drug metabolism.

Effects of an adjunctive treatment with Bacillus subtilis for food allergy

The authors evaluated the clinical efficacy of an adjunctive treatment with spores of Bacillus subtilis in 20 adult patients with urticaria-angioedema syndrome from food allergy. The patients treated with B. subtilis showed a significant reduction in frequency and severity of clinical features in respect to the patients who received no treatment. Bacillus subtilis spores may increase S-IgA synthesis or protect gastroenteric mucosa.

Comparative effects of H2-receptor antagonists on drug interaction in rats

The most widely used H2-receptor antagonist, cimetidine, is known to interact with cytochrome P-450 drug-metabolizing enzymes and, therefore, interacts with other drugs which may be administered concurrently. In this study, effects of three H2-receptor antagonists, famotidine, ranitidine, and L-643,441, on drug interaction were studied using cimetidine as a positive control. Cimetidine and L-643,441, but not famotidine or ranitidine, prolonged antipyrine elimination and hexobarbital-induced sleeping time. The effect of cimetidine and famotidine on the anticoagulant effect on warfarin in rats was also investigated. Pretreatment of rats with cimetidine produced a significant depression of plasma prothrombin complex activity, whereas concomitant administration of famotidine did not alter the plasma prothrombin complex activity. Whereas cimetidine is known to impair the elimination of a number of drugs metabolized by microsomal mixed function oxidase enzyme systems, the results of the present study suggest that famotidine and ranitidine have little effect on these enzyme systems.

Pharmacology of the novel H2 antagonist famotidine: in vitro studies

The novel antiulcer drug famotidine was found to be a potent and selective inhibitor of histamine H2 receptors. Its activity on different parameters involving H2 receptors was higher than that of other compounds of the family: pA2 values were 8.33, 7.86 and 7.83 in the guinea pig atria, guinea pig papillary muscle and isolated rat gastric secretion, respectively. Apart from quantitative differences, famotidine differed from the other compounds, since it caused a competitive antagonism only at low concentrations and an unsurmountable antagonism at higher concentrations. The duration of the inhibitory action on the "in vitro" gastric secretion resembled that of cimetidine and ranitidine. Famotidine was highly effective (approximately 10 times as potent as ranitidine) also on the rat uterus (unsurmountable antagonism) and on the guinea pig gallbladder (pA2 value = 7.71). Famotidine was apparently devoid of non-specific effects concerning the gastrointestinal motility even at very high concentrations (10(-4) M). In this respect, famotidine appeared to be more selective than cimetidine and ranitidine at the H2 receptor level. The high potency, the peculiarity of the antagonism and the lack of side-effects on a number of isolated preparations, indicate this H2 antagonist as a very peculiar member of the group.

Inhibitory effect of famotidine on cat gastric secretion

The inhibitory effect of the novel H2 receptor antagonist famotidine was studied in conscious gastric fistula cats against dimaprit-induced hypersecretion, in comparison with ranitidine. On the secretory plateau induced by dimaprit (2 mumol kg-1 h-1) famotidine (0.05-0.2 mumol kg-1 i.v.) exerted a dose-dependent inhibitory effect, being approximately 4.5 times as potent as ranitidine (ID50 values were 0.067 +/- 0.015 and 0.30 +/- 0.025 mumol kg-1 for famotidine and ranitidine, respectively). No significant differences were found between the two drugs, as for the time-course of the inhibitory effect. Famotidine (0.01-0.32 mumol kg-1 h-1) caused a parallel displacement of the dose-response curve to dimaprit to the right, without reducing the maximum response to the stimulant, thus behaving as a competitive antagonist, like ranitidine. pA2 values for famotidine and ranitidine were 7.95 and 6.92, respectively. In the same range of doses famotidine dose-dependently reduced also the secretory response to histamine. From these data it was concluded that famotidine is a potent histamine H2 receptor antagonist in the cat gastric mucosa; moreover, conversely from "in vitro" data, the antagonism was surmountable even at the highest doses tested. In vivo experiment, therefore, did not reveal any particular feature of this compound, apart from the undoubtedly high potency, in comparison with other members of the family.

Comparison of effects of oral and intravenous famotidine on inhibition of nocturnal gastric acid secretion

In this double-blind, placebo-controlled, four-way crossover, randomized study, eight high-secretor (more than 5 meq per hour) volunteers received 20 mg of famotidine by mouth, 10 mg intravenously, and 20 mg intravenously at 9 P.M. Volume, acid content, and pH of continuous gastric aspirates were measured hourly from one to at least 12 hours after treatment. Plasma concentrations of famotidine were determined at specified intervals. All famotidine doses produced marked suppression of gastric secretion. The mean total output was 1,196.3, 526.8, 414.9, and 518.0 ml for placebo, the 10-mg intravenous famotidine dose, the 20-mg intravenous dose, and the 20-mg oral dose, respectively. The latter three values were significantly different from that of placebo at p less than 0.01. The mean total acid output was 105.3, 8.3, 2.3, and 6.2 meq, respectively, and the acid output for all three doses was significantly different from that of placebo at p less than 0.01. The onset of antisecretory effect was noted as early as one hour after dosing. The mean gastric aspirate pH values were 1.7, 5.5, 6.2, and 4.4 during the second hour after placebo, the 10-mg intravenous dose, the 20-mg intravenous dose, and the 20-mg oral dose, respectively, with the treatment pH values significantly different from the placebo pH value at p less than 0.01. Higher mean pH values were reached at seven, eight, and nine hours after the 20-mg intravenous dose than after the 10-mg intravenous dose (p less than 0.05). By the 12th hour after administration of the 10-mg intravenous dose, pH values had returned to baseline in all but one subject. After the 20-mg intravenous dose, a similar loss of effect occurred in one subject at 12 hours and in all subjects by 15 hours. Plasma concentrations of famotidine greater than 50 ng/ml were associated with an acid output inhibition of more than 80 percent, whereas high (more than 90 percent) as well as low (less than 50 percent) inhibition was observed at famotidine concentrations below 50 ng/ml.

Famotidine in the therapy of gastric hypersecretory states

The histamine (H2)-receptor antagonist famotidine was compared with ranitidine and cimetidine in its ability to control gastric acid hypersecretion in 33 patients with gastric hypersecretory states (32 patients with Zollinger-Ellison syndrome and one patient with idiopathic hypersecretion). Equipotent doses of each drug were determined in nine patients and used to determine relative onset of action, duration of action, and potency. Each drug had a similar time course of onset with a maximal effect at three to four hours after oral ingestion. The duration of action of famotidine was 30 percent longer than that of either cimetidine or ranitidine. In terms of relative potency, famotidine was nine times more potent than ranitidine and 32 times more potent than cimetidine. Thirty-two patients underwent long-term famotidine treatment for up to 34 months (mean, 10 months) with a duration in 21 patients of at least six months, in nine patients of at least 12 months, and in six patients of at least 24 months. The mean daily maintenance dose with famotidine was 0.33 g per day (range, 0.05 to 0.8 g). Prior to famotidine therapy, 27 patients were taking ranitidine and the mean daily dose required was 2.3 g per day (range, 0.6 to 5.4 g), whereas six patients were taking cimetidine and the mean daily dose was 4.6 g per day (range, 1.2 to 9.0 g). Fourteen of the 32 patients required an anticholinergic agent in addition to ranitidine or cimetidine to maintain control, whereas only five patients required an anticholinergic agent with famotidine. Gastric acid hypersecretion was controlled in seven patients with less frequent dosing with famotidine than with cimetidine or ranitidine. Long-term treatment with famotidine was not associated with any hematologic or biochemical toxicity or clinical side effects. These results demonstrate that famotidine has a similar onset of action to other H2-receptor antagonists but has a 30 percent longer duration of action and is nine times more potent than ranitidine and 32 times more potent than cimetidine. Famotidine is safe and highly effective in the long-term treatment of gastric hypersecretory states.

A multicenter, randomized, double-blind study comparing famotidine with ranitidine in the treatment of active duodenal ulcer disease

Famotidine, a new long-acting histamine (H2)-receptor antagonist, has recently been shown to be more effective than placebo in healing active duodenal ulcer. In the current study, the efficacy and tolerability of famotidine were further investigated and compared with those of ranitidine in a multicenter, double-blind, randomized international study. Sixty-eight investigators from 19 countries enrolled 1,031 patients with endoscopically proven active duodenal ulcers. Patients received either ranitidine (150 mg twice daily) or famotidine at one of three different dosage regimens: 40 mg at bedtime, 40 mg twice daily, or 20 mg twice daily. Ulcer healing was assessed by serial endoscopy with pain relief and safety profiles also closely monitored. Nine hundred and eighty patients fulfilled the evaluation criteria. During the eight-week study, there was no significant difference in ulcer healing rates between the ranitidine control group and any of the famotidine treatment groups. At eight weeks, the healing rates were 87, 92, 92, and 90 percent for the famotidine (40 mg at bedtime, 20 mg twice daily, and 40 mg twice daily) and ranitidine groups, respectively. Ulcer pain improved and antacid consumption decreased in all the groups equally. The clinical and safety profiles were also similar in all four groups. This study indicates that famotidine used once or twice a day is as effective and well tolerated as twice-a-day ranitidine in the treatment of active duodenal ulcers, with the recommended dosage being 40 mg at bedtime. Furthermore, these data emphasize the importance of nocturnal acid secretion in the pathophysiology of duodenal ulcer disease.

Maintenance therapy of duodenal ulcer with famotidine. A multicenter United States study

The decision to treat a patient with duodenal ulcer should be based upon the following: severity of disease; effectiveness of treatment; and risk and cost of treatment. A number of drugs are effective for this condition. When administration of the drug is discontinued, a recurrence of the ulcer occurs most often within three months, with the rate approaching 90 percent at one year. Maintenance therapy has evolved as a method of preventing recurrence. A double-blind, randomized, multicenter study was done to compare 40 mg of famotidine at bedtime, 20 mg of famotidine at bedtime, and placebo in the maintenance treatment of patients with recently healed duodenal ulcer. In 37 centers in the United States, 303 patients received randomly allocated treatment with 40 mg of famotidine at bedtime (107 patients), 20 mg of famotidine at bedtime (97 patients), or placebo (99 patients). The treatment groups were comparable as to the risk factors and other characteristics. Esophagogastroduodenoscopies were scheduled at three, six, and 12 months of treatment. Additional endoscopies could be done at any time if symptoms suggested a relapse. Cumulative relapse rates were significantly lower in the famotidine groups than in the placebo group at all time points (p less than 0.01). The cumulative life-table relapse rates at three, six, and 12 months were 9.2, 20.9, and 24.8 percent for the 40-mg famotidine group; 13.5, 16.1, and 23.3 percent for the 20-mg famotidine group; and 39.3, 51.5, and 56.8 percent for the placebo group. No significant difference between the two famotidine groups was observed. Within each period, the relapse rate was lower with famotidine than with placebo. Famotidine is more effective than placebo as maintenance therapy. It is generally well tolerated for periods of up to one year. A dose of 20 mg at bedtime is proposed as the maintenance dose. Fewer relapses occurred in non-smokers, in females, and in patients in whom healing occurred with placebo. More relapses occurred in patients under 40 years of age, patients with a long ulcer history, or patients who were younger than 40 years of age at onset of ulcer disease.

Famotidine: an appraisal of its mode of action and safety

Famotidine is a potent histamine (H2)-receptor antagonist that binds to the H2 receptor in a competitive reversible manner as shown by in vivo, in vitro, and clinical studies. Famotidine has shown no evidence of carcinogenicity, mutagenicity, or teratogenicity in extensive and adequately designed safety assessment studies. The drug produces neither prolonged anacidity nor doses its use result in significant elevations of serum gastrin levels beyond those seen with other available H2-receptor antagonists when used as recommended for the treatment of ulcer disease. Taken together, these data demonstrate no undue or disproportionate risk to the use of famotidine.

Efficacy and safety of famotidine in the management of benign gastric ulcers

The worldwide experience with famotidine in the management of benign gastric ulcers is reviewed. Analysis of data from 15 countries has shown that famotidine is more effective than placebo in treating gastric ulcers. Relief of pain is achieved earlier in famotidine-treated patients. Complete endoscopic healing may be expected in 64 to 80 percent of patients within eight weeks following the initiation of therapy. Response to famotidine does not appear to be affected by age, sex, smoking, regular alcohol consumption, or duration of disease. Short-term oral famotidine, at a dose of 40 mg daily, is well tolerated, and there have been no serious adverse experiences attributed to its administration. The efficacy of famotidine is comparable to that of other histamine (H2)-receptor antagonists.

Pharmacodynamics of famotidine in humans

The physiologic role of histamine (H2) receptors and their involvement in pharmacologic responses have not been completely defined. To date, H2-receptor-specific pharmacologic actions of H2-receptor inhibitors in humans are primarily associated with effects on gastric acid secretion. Famotidine is a new potent competitive inhibitor of H2 receptors. During its development, in addition to studies defining its gastric acid antisecretory profile, famotidine was also examined for potential effects on other functions of the gastrointestinal tract and on other systems. Famotidine inhibits basal and stimulated gastric acid secretion in a dose-dependent manner after oral administration of 5 to 40 mg. Maximal effect is achieved by the 40-mg dose, with peak activity reached one to three hours after dosing and a duration of action lasting 10 to 12 hours. Gastric emptying times and exocrine pancreatic function are not affected after famotidine (40 mg twice daily) treatment. Blood pressure, heart rate, and electrocardiographic patterns remain unchanged after oral or intravenous administration of famotidine in doses up to 40 mg and 20 mg, respectively. Serum prolactin levels do not rise after intravenous administration of 20 mg of famotidine. The levels of prolactin, testosterone, dehydroepiandrosterone, follicle-stimulating hormone, luteinizing hormone, and other circulating hormones remain unchanged during four weeks of treatment with famotidine 40 mg daily. Renal inulin and creatinine clearances show no change after intravenous administration of 10 mg of famotidine, and tubular excretion of procainamide and its major metabolite is unchanged after administration of 40 mg of famotidine. No significant effects are found on the biologic disposition of theophylline, warfarin, and other compounds metabolized by the liver cytochrome P450 enzyme system when they are given concomitantly with famotidine.

Treatment of active duodenal ulcers with famotidine. A double-blind comparison with ranitidine

In a double-blind multicenter trial, 100 patients with active duodenal ulcer were treated with a single nocturnal dose of famotidine 40 mg or ranitidine 300 mg. Antacid tablets were allowed as additional treatment if needed for pain relief. Endoscopy was repeated after two weeks, and again after four weeks if the ulcer had not healed earlier. Two patients in the famotidine group were withdrawn from the study because of non-compliance with the protocol. After two weeks, ulcers in 64 percent of the patients receiving famotidine and 46 percent of the patients receiving ranitidine were healed (p = 0.072). After four weeks, healing rates were 94 percent (famotidine) and 90 percent (ranitidine). Pain relief was rapid in either treatment group, with a tendency for better response during the day in the famotidine group. Mean antacid consumption during the first week was 3.0 tablets (34.5 mmol) in the famotidine group and 4.1 tablets (47.2 mmol) in the ranitidine group. Famotidine provides excellent healing and relief of symptoms in patients with duodenal ulcer disease.

Comparison of the effects of gastric antisecretory agents in healthy volunteers and patients with duodenal ulcer

Thirty published studies of the clinical pharmacology of gastric antisecretory agents in normal volunteers and duodenal ulcer patients were reviewed. The aim was to investigate the relationship between antisecretory effect in the two populations. There was a significant correlation between effect in patients and normal subjects for suppression of 24 hour intragastric acidity (r = 0.732; p = 0.0068), nocturnal intragastric acidity (r = 0.861; p = 0.0033) and nocturnal acid output (r = 0.964; p = 0.0069). The regression lines for 24 hour and nocturnal acidity were very similar. The expected antisecretory effect of a particular dosage regimen in patients with duodenal ulcer can be predicted mathematically from data derived from studies in normal volunteers.

Famotidine. Pharmacodynamic and pharmacokinetic properties and a preliminary review of its therapeutic use in peptic ulcer disease and Zollinger-Ellison syndrome

Famotidine is a new histamine H2-receptor antagonist. On a weight basis, famotidine is 20 times more potent than cimetidine and 7.5 times more potent than ranitidine in inhibiting basal and pentagastrin-stimulated gastric acid secretion in humans. Therapeutic trials have shown that famotidine 20 mg twice daily or 40 mg at bedtime may be an effective alternative to standard doses of cimetidine for healing gastric ulcers and to standard doses of cimetidine and ranitidine for healing duodenal ulcers. When used prophylactically, a single 20 mg dose of famotidine at night decreases the incidence of duodenal ulcer recurrence (versus placebo). However, further study is needed to clarify the comparative efficacy of the H2-receptor antagonists, in particular as maintenance therapy for healed peptic ulcer. Preliminary results in a few patients with Zollinger-Ellison syndrome indicate that famotidine, alone or in combination with an anticholinergic agent, gives good control of gastric acid hyperacidity with no evidence of biochemical or haematological toxicity. Famotidine appears to be well tolerated. Unlike cimetidine, it does not have antiandrogenic effects or alter hepatic metabolism of drugs. However, wider clinical experience with famotidine is needed to accurately determine its relative tolerability compared with other anti-ulcer drugs. Thus, famotidine appears to be a suitable and well tolerated alternative to cimetidine and ranitidine for healing peptic ulcers, but wider clinical experience is needed to assess its relative efficacy and tolerability in the long term maintenance treatment of patients with healed ulcers as well as in patients with Zollinger-Ellison syndrome.

Reversed-phase determination of famotidine, potential degradates, and preservatives in pharmaceutical formulations by high-performance liquid chromatography using silica as a stationary phase

An analytical method was developed for the determination of famotidine, potential degradates, and preservatives in several pharmaceutical formulations. The method employs reversed-phase chromatography on a silica column with a methanol-phosphate solution as the mobile phase. The influence of the concentration of phosphate and organic modifier are discussed. Accuracy and precision for this method along with assay data from different formulations of famotidine are presented. Two different commercial silica columns were tested with this method. Chromatographic differences related to the surface area and pore size of the silica are discussed.

Effect of H2-receptor antagonists on acetaminophen-induced hepatic injury

The effects of H2-antagonists on acetaminophen-induced hepatic injury were examined. Rats were administered acetaminophen at the dose of 800 mg/kg body, 60 hr after injection of 3-methylcholanthrene. As an H2-antagonist, cimetidine (200 mg/kg), ranitidine (50 mg or 100 mg/kg), or famotidine (20 mg or 40 mg/kg) was administered before and after acetaminophen injection. The group administered only acetaminophen had been severely damaged as evaluated by changes in serum transaminase, P-450 content, aminopyrine demethylation, glutathione content and histological study, but administration of 200 mg cimetidine together with acetaminophen significantly reduced the hepatic injury to nearly the control level. Ranitidine had no protective effect against hepatic injury at the dose of 50 mg, which appears to have the same antacid effect as 200 mg cimetidine, whereas it had a slight but significant protective effect as evaluated by the transaminase level, glutathione content and histological study at the dose of 100 mg. Famotidine had no effect against acetaminophen induced hepatic injury. Because famotidine had no effect, the protection by H2-antagonist against acetaminophen-induced hepatic injury cannot be explained by the decrease in hepatic blood flow alone. Therefore, inhibition of P-450 activity seems to be more important for reducing the generation of the reactive metabolites of acetaminophen than hepatic blood flow decrease.

Interaction of famotidine with rat liver microsomes, a study showing less inhibition of drug metabolism than with cimetidine

Interaction of famotidine with rat liver microsomes and its effect on drug metabolism in vitro were studied. Famotidine interacted with liver microsomes obtained from untreated, phenobarbital-pretreated and 3-methylcholanthrene-pretreated rats to produce characteristic type II spectral changes with peaks at 423-426 nm and troughs at 387-390 nm. The spectral dissociation constants were in the range of 0.84-0.94 mM. Famotidine inhibited aminopyrine N-demethylase activity to a much lesser extent than did cimetidine. The extent of inhibition at a concentration of 5 mM of famotidine was from 12 to 18% for the microsomes from the rats with different pretreatments. In contrast, 5 mM of cimetidine inhibited the activity 80, 59 and 80% in the microsomes from untreated, phenobarbital-pretreated and 3-methylcholanthrene-pretreated rats, respectively. Both famotidine and cimetidine inhibited aminopyrine N-demethylase in a mixed-type manner for the microsomes from phenobarbital-pretreated rats, with inhibition constants of 4.7 and 0.7 mM, respectively. These results demonstrate that famotidine is an in vitro inhibitor of microsomal drug metabolism in rats but is much less inhibitory than cimetidine.

Cholinergic effects of histamine-H2 receptor antagonists partly through inhibition of acetylcholinesterase

The effects of histamine H2-receptor antagonists on acetylcholinesterase and pseudocholinesterase activity were studied. All H2-antagonists tested inhibited both enzyme activities dose-dependently. The potency of inhibitory activity of H2-antagonists on acetylcholinesterase estimated from median inhibitory dose were in the following order of decreasing activity: ranitidine greater than TZU-0460 greater than cimetidine greater than YM-11170, whereas that on pseudocholinesterase were TZU-0460 greater than ranitidine greater than cimetidine greater than YM-11170. As the effects derived from the inhibition of acetylcholinesterase by H2-antagonists may affect intestinal motility, we studied ileal muscle contractions. Ranitidine had the most potent stimulating effect on contraction, the pattern of which was similar to physostigmine and was blocked by atropine and morphine. YM-11170 had a weak action on muscle contraction and cholinesterase activities.

Interaction of diazepam with famotidine and cimetidine, two H2-receptor antagonists

Famotidine is currently under investigation as an H2-receptor antagonist. Eleven healthy male volunteers received a single 10 mg intravenous dose of diazepam on three occasions: once during coadministration of famotidine 40 mg bid, once during coadministration of cimetidine 300 mg qid, and once without other drug treatment (control). Multiple blood samples were drawn during the seven days after each diazepam dose. Diazepam and desmethyldiazepam plasma concentrations were measured by electron capture gas chromatography. There were no significant differences among the three treatment conditions in diazepam central compartment volume or total volume of distribution. During the cimetidine as compared with the control treatment, diazepam elimination half-life was significantly increased (72 vs 55 hr, P less than .05), total area under the curve (AUC) increased (11.8 vs 9.8 hr-micrograms/mL, P less than .05), and total clearance reduced (0.20 vs 0.28 mL/min/kg, P less than .05). Seven-day AUC for desmethyldiazepam also increased (4.6 vs 3.8 hr-micrograms/mL, P less than .05). However, there were no significant differences between famotidine and control treatment conditions in diazepam elimination half-life (53 vs 55 hr), total AUC (9.5 vs 9.8 hr-micrograms/mL), or total clearance (0.28 vs 0.28 mL/min/kg) or in seven-day AUC for desmethyldiazepam (3.9 vs 3.8 hr-micrograms/mL). Thus, therapeutic doses of cimetidine significantly impair the clearance of diazepam and desmethyldiazepam. Therapeutic doses of famotidine do not impair diazepam and desmethyldiazepam kinetics, suggesting that there is no significant kinetic interaction when diazepam and famotidine are administered concurrently in clinical practice.

Bacterial genotoxicity of nitrosated famotidine

Famotidine, a histamine H2-receptor antagonist, was devoid of mutagenic activity in seven his- Salmonella typhimurium strains (TA1535, TA1537, TA1538, TA97, TA98, TA100 and TA102) and was equitoxic in repair-proficient (WP2) and repair-deficient (WP2uvrA, WP67, CM561, CM571, WP100 and CM871) Escherichia coli strains, both in the presence and in the absence of S9 mix containing liver S9 fractions from Aroclor-treated rats. However, after a short pre-incubation step with nitrite in an acidic environment, the drug increased, by a direct mechanism, the number of his+ revertants in Salmonella strains TA100, TA102 and TA97 (a decrease of mutagenicity being conversely observed in TA1535) and of trp+ revertants in E. coli strains WP2uvrA and WP67. Moreover, it enhanced the induction of non-reparable DNA damage in E. coli strains simultaneously lacking the uvrA-dependent excision repair and the lexA post-replication repair pathways. The mutagenicity of acidified nitrite-famotidine mixtures was related to doses of both precursors, with a maximum production of mutagenic derivatives in a slight molar excess of nitrite. The optimal pH of the nitrosation reaction (2.0) was intermediate between the one required for cimetidine (1.5) and ranitidine (2.5). Potency of famotidine as a precursor of mutagenic derivatives was considerably lower than the one of the other two H2 blockers. The nitrosation products of all three drugs mainly induced base-pair substitutions in Salmonella DNA, to a greater extent at sites containing G.C base pairs (strain TA100) in the case of famotidine and cimetidine, and at sites containing A.T base pairs (TA102) in the case of ranitidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamics of the gastric mucosa and gastric ulceration in rats and in patients with gastric ulcer

The microcirculation is the fundamental nutrient supply and waste removal system of all tissues. Recent improvements in spectrophotometric technique have made possible the noninvasive assessment of oxygen supply and utilization in the gastric mucosa. The authors have utilized such methods to assess gastric mucosal hemodynamics. The technique permitted further clarification of the roles of the gastric microcirculation, mucosal oxygenation, and acid secretion in the pathogenesis of stress ulcers in the stomach of rats. Furthermore, it provided important information on the function of gastric mucosal hemodynamics in the healing of gastric ulcers in man. The technique is described along with the authors' correlation studies between spectrophotometric data and other techniques for measuring gastric blood flow (hydrogen gas clearance and aminopyrine clearance methods and direct electromagnetic flowmeter techniques) and the prevention of ulcerogenesis.