The effect of H2-receptor antagonists on antipyrine and pentobarbital metabolism in male and female rats

Pretreatment of male and female rats with cimetidine decreased the amount of 3-hydroxymethylantipyrine in the 24-hr urine, but urinary antipyrine and 4-hydroxyantipyrine were increased compared to that of the corresponding control rats. On the other hand, the amount of norantipyrine and the total amount of antipyrine and its metabolites were not changed by cimetidine, ranitidine and famotidine. These data suggest that ranitidine and famotidine have little effect on the microsomal mixed function oxidase system in male and female rats.

Kinetic studies on the competition between famotidine and cimetidine in rats. Evidence of multiple renal secretory systems for organic cations

The H2-receptor antagonists famotidine and cimetidine are both basic drugs that are predominantly eliminated by the kidneys. Cimetidine has been shown to inhibit the renal secretion of tetraethyl-ammonium bromide (TEAB) but not p-aminohippuric acid (PAH), suggesting that cimetidine is secreted by an organic cation transport system [Weiner and Roth: J. Pharmacol. Exp. Ther. 216: 516 (1981)]. The present study shows that famotidine behaves like cimetidine in that it also inhibits TEAB but not PAH excretion. Where a high concentration of cimetidine in plasma has an inhibitory effect on the renal excretion of famotidine, the reverse is not true, i.e. high plasma levels of famotidine have no effect on the excretion of cimetidine. Further evidence that additional transport systems are involved in the renal tubular secretion of cimetidine is as follows. Quinine, a potent competitor of the organic cation transport system, inhibits the secretory component of famotidine renal clearance but not that of cimetidine. Probenecid, a classic competitor for the organic anion transport system, inhibits the renal excretion of cimetidine but not famotidine. However, the effect of probenecid is minor and not sufficient to account for other components of cimetidine secretion not affected by famotidine and quinine.

Double blind comparison of the effects of cimetidine, ranitidine, famotidine, and placebo on intragastric acidity in 30 normal volunteers

Continuous measurement of 24 hour intragastric acidity was carried out in 30 normal volunteers during treatment with placebo, cimetidine 800 mg, ranitidine 300 mg, and famotidine 40 mg in a double blind study. Medication was taken after the evening meal (post cenam nocte, PCN). Median 24 hour acidity decreased with all H2-receptor antagonists from 25.1 mmol/l on placebo to 10 mmol/l (-60.1%) during cimetidine, to 3.2 mmol/l (-87.25%) during ranitidine and to 2.5 mmol/l (-90.0%) during famotidine treatment (p less than 0.0005). All drugs significantly inhibited night time acidity but only famotidine decreased acidity during the late morning compared with placebo. Significantly greater acid reduction was seen with famotidine and ranitidine compared with cimetidine but no difference was found between famotidine and ranitidine.

Effects of age and chronic renal failure on the urinary excretion kinetics of famotidine in man

The plasma and urine concentrations of famotidine, a new, potent H2-receptor antagonist, have been measured in 16 healthy young adults, 8 healthy elderly people and 18 patients with varying degrees of renal dysfunction after intravenous administration. Both the plasma elimination and renal excretion of famotidine were decreased in the elderly volunteers and renal patients. The renal clearance of famotidine averaged 4.43 ml/min/kg (310 ml/min) in normal young volunteers, which exceeded the mean creatinine clearance 1.55 ml/min/kg (109 ml/min), suggesting net secretion is a significant mechanism for elimination of famotidine. The ratio of famotidine renal clearance to creatinine clearance decreased as creatinine clearance decreased; these results suggest that the deterioration in the secretion process was much faster than that in glomerular filtration and are incompatible with the "intact nephron hypothesis". Nevertheless, both total body clearance and renal clearance were significantly correlated with creatinine clearance. The apparent half-life was also significantly correlated with creatinine clearance. Since famotidine is essentially free of dose-related adverse effects, dose adjustment in patients with mild renal insufficiency and in elderly people is not required; however, either a prolonged dosing interval or a decrease in daily dose during long-term therapy may be adapted for the patients with severe renal insufficiency to avoid accumulation and the potential undesirable effects.

Famotidine versus cimetidine in the treatment of acute duodenal ulcer. Double-blind, randomized clinical trial comparing nocturnal administration of 40 mg famotidine to 800 mg cimetidine

The efficacy of famotidine, a potent new long-acting H2 receptor antagonist, was compared with cimetidine in 78 patients with endoscopically proven acute duodenal ulcers. Additional antacid self-medication was allowed if needed for relief of pain. Thirty-nine patients were allocated to each group, receiving a nocturnal oral dose of either 40 mg famotidine or 800 mg cimetidine. Patients were reassessed by endoscopy at 2, 4 and 6 weeks if ulcer healing had not occurred at the respective earlier control date. A diary was kept to record the duration and intensity of day and night pain and the amount of antacids ingested. After 2 and 4 weeks of treatment healing rates were not significantly different for either group (famotidine 31 and 95%, cimetidine 23 and 85%, respectively). Pain relief was rapid in both treatment groups with a tendency for better response of nighttime pain in famotidine-treated patients. Antacid consumption was not different in either group. Famotidine appears to be an effective treatment for acute duodenal ulcer. Compared to cimetidine, healing rates and relief of pain are not significantly different.

Pharmacokinetics of histamine (H2)-receptor antagonists, including roxatidine, in chronic renal failure

In this paper the effects of chronic renal failure on the pharmacokinetics of H2-antagonists are reviewed and the results obtained with roxatidine presented. In normal renal function renal clearance is around 60-80% of total plasma clearance of all H2-antagonists. Consequently, prolongation of serum half-life, mainly due to a decrease in urinary excretion, is noted in patients with decreasing glomerular filtration rate. In chronic renal failure, a dose reduction is therefore necessary with all H2-antagonists, including roxatidine. It appears that neither haemodialysis nor peritoneal dialysis substantially influences the pharmacokinetics of these drugs. Therefore, the same dosage schedule as in uraemia may be applied in patients with dialysis. Finally, in the elderly the dosage of all H2-antagonists should be adapted to the expected decrease in renal function.

Famotidine has no significant effect on gonadal function in man

The effect of a single bedtime dose of famotidine 40 mg on gonadal function was studied in 8 male duodenal ulcer patients. The drug was orally administered for 4 weeks. Our results show that this new H2 blocker influences basal and stimulated serum levels of neither testosterone nor gonadotrophins (LH, FSH). Besides, no significant variations were observed before and after famotidine treatment in seminal fluid characteristics evaluated in 5 out of 8 cases. It can be concluded that famotidine appears to leave gonadal function unaffected in man.

A comparison of the effects on intragastric acidity of bedtime or dinnertime administration of a once daily dose of famotidine

In order to assess whether dinnertime administration of a once daily dose of famotidine is more advantageous than a bedtime dose in suppressing evening and nocturnal gastric acidity, we gave nine patients with a past history of duodenal ulcer in double-blind, randomized fashion either (1) placebo at 6 p.m. and 10 p.m., (2) famotidine 40 mg at 6 p.m. (Fam 6) + placebo at 10 p.m. or (3) placebo at 6 p.m. + famotidine at 10 p.m. (Fam 10) on three separate occasions. Comparison of the 24-h median pH values showed that the two administrations of famotidine were superior to placebo, while Fam 6 was significantly more effective than Fam 10. The gain in acid suppression of Fam 6 with respect to Fam 10 was particularly evident from 6 p.m. to midnight. Although the antisecretory effectiveness of Fam 6 was lower than that of Fam 10 from 4 a.m. to 8 a.m., it remained clearly higher than that of placebo and ensured virtual anacidity (median pH = 6.7) even in this time segment. We conclude that a once daily dose of famotidine at 6 p.m. is better than bedtime administration at covering the long period of continuous unbuffered intragastric acidity which extends from after the evening meal to breakfast.

[Double-blind study on the effects of famotidine on bronchial tone and on expectoration]

A double blind test using famotidine and a placebo was conducted on 14 patients with hypersecretory, chronic bronchitis. No other drug treatment was given during the test or in the ten days preceding it. VC, FEV1, Sgaw and daily excrete volume were measured before the test and 7, 14 and 21 days after it began. The data collected indicate that H2 receptors have no influence on bronchial calibre or secretions.

Effects of histamine and its blocker on thyrotropin releasing hormone release from rat adrenal gland in vitro

The effects of histamine and its blocker on the release of thyrotropin releasing hormone (TRH) from the rat adrenal gland were studied in vitro. Rat adrenals were incubated in medium 199 with 1.0 mg ml-1 of bacitracin and 100 micrograms ml-1 of ascorbic acid (pH 7.4) for 20 min and TRH released into the medium was measured by radio-immunoassay. The immunoreactive TRH (ir-TRH) release from the rat adrenal gland was inhibited significantly in a dose-related manner by the addition of histamine and enhanced by the addition of famotidine. The effect of histamine on ir-TRH release from the rat adrenal gland was blocked by the addition of famotidine to the medium, but not by that of mepyramine. The elution profile of methanol extracted adrenal gland on Sephadex G-10 was identical to that of synthetic TRH. The findings suggest that histamine inhibits TRH release from the rat adrenal gland and that its effects may be mediated via H2-receptor.

H2-receptor antagonists and duodenal ulcer recurrence: analysis of efficacy and commentary on safety, costs, and patient selection

Maintenance treatment to prevent duodenal ulcer recurrence has been studied in more than 100 trials. These trials, together with reports of long-term safety of maintenance therapy, risk factors of ulcer recurrence, and economic implications of different strategies of long-term ulcer management have been analyzed. Recurrence rates with the FDA-approved drugs for maintenance therapy, cimetidine, ranitidine, and famotidine are comparable when compared as "weighted" or "unweighted" means. H2-blockers reduce the annual recurrence from nearly 70% to about 25%. The duration of maintenance treatment is uncertain, but probably should not be less than 1 yr. Cimetidine maintenance for up to 5 yr has not disclosed new side effects, and the rate of reactions decreases after the first yr. Maintenance is economically superior to intermittent treatment or surgery in the ulcer population, but long-term management should be individualized according to risk factors for recurrence.

Effect of mifentidine on mepirizole-induced duodenal ulcer in the rat

The H2-receptor antagonists mifentidine, famotidine, cimetidine and ranitidine were examined for their ability to prevent the duodenal ulcer caused by mepirizole (250 mg/kg p.o.), a non-steroidal anti-inflammatory agent, in the conscious rat. All the compounds exerted a dose-related protective effect and on the basis of their ED50s, the following rank order of potency was found: mifentidine = famotidine greater than ranitidine greater than cimetidine. The antiulcer activity displayed by the H2-receptor antagonists evaluated in this model reflects their potency in inhibiting basal and stimulated gastric acid secretion in rat. The results of these studies indicate mifentidine as a potent anti-ulcer agent.

Single-dose pharmacokinetics and bioavailability of famotidine in man. Results of multicenter collaborative studies

Pharmacokinetics and bioavailability of famotidine, a new H2-receptor antagonist, were investigated in healthy subjects in five clinical studies. Linear pharmacokinetics were observed following either intravenous or oral administration. Plasma clearance averaged 463 ml min-1. Renal clearance averaged 310 ml min-1, which exceeded the glomerular filtration rate. Renal excretion was the major route of elimination. Urinary recovery of unchanged drug following intravenous administration was about 67 per cent. Famotidine plasma half-life was approximately 2.6 h. Oral absorption was incomplete. The bioavailability averaged 43 per cent of the dose.

Comparative effect of famotidine and cimetidine on the pharmacokinetics of theophylline in normal volunteers

The comparative effect of famotidine or cimetidine on theophylline disposition was determined in healthy volunteers. Cimetidine, but not famotidine, caused a reduction in the rate of elimination of theophylline. The mean total body clearance of theophylline was reduced from 57.6 ml min-1 before cimetidine to 39.5 ml min-1 during cimetidine; and the half-life was prolonged from 8.7 h before cimetidine to 12 h during cimetidine. The volume of distribution and renal excretion of theophylline were not affected by either famotidine or cimetidine.

[Does a single oral dose of famotidine influence the blood alcohol level?]

Six healthy volunteer medical students (three men and three women) on four separate occasions drank 500 ml of beer or 250 ml of white wine 30 min after having taken 40 mg of famotidine or a placebo (after 48 hours of abstinence and six hours of fasting). Administration of drug or placebo followed a double-blind, randomized protocol. There was no demonstrable effect of famotidine on the serum level of alcohol (maximal values 0.29-0.67 mg/dl) or on the time until maximal serum concentrations of alcohol were reached.

Studies on histamine H2 receptor antagonists. 2. Synthesis and pharmacological activities of N-sulfamoyl and N-sulfonyl amidine derivatives

A series of N-sulfamoyl and N-sulfonyl amidines have been prepared and tested in vitro for H2 antihistamine activity on guinea pig atrium. In addition, several selected compounds were assessed as inhibitors of gastric acid secretion induced by histamine in anesthetized dogs. Structure-activity relationship studies showed that those compounds containing 2-[(diaminomethylene)amino]thiazole exhibited potent H2-receptor antagonist activity. Introduction of alkyl or aralkyl groups to the terminal nitrogen of the sulfamoyl moiety reduced biological activities. Sulfamoyl amidines were more potent in both tests than sulfonyl amidines. Of these compounds, 3-[[[2-[(diaminomethylene)amino]-4-thiazolyl]methyl]thio]- N2-sulfamoylpropionamidine (2e, famotidine) showed extremely high potency in both assays and was selected for clinical trials as an antiulcer agent. Acid-catalyzed hydrolysis of famotidine gave the sulfamoyl amide 6 at room temperature and the carboxylic acid 7 at elevated temperatures. 15N NMR spectrum showed that famotidine in solution existed in only one of several possible tautomers derived from the amidine and the guanidine moieties. Nitrosation of famotidine was performed under mild condition and proved to occur on the 5-position of the thiazole ring.

Disposition of famotidine in renal insufficiency

The disposition of famotidine was evaluated in 18 patients; Group 1, mild renal insufficiency, [creatinine clearance (CLCR): 30-60 mL/min]; Group 2, moderate to severe renal insufficiency (CLCR: 10-30 mL/min); Group 3, end-stage renal disease requiring maintenance hemodialysis (anuric). Blood and urine samples were obtained over a 72-hour period. Plasma concentration-time data demonstrated biexponential decay. The terminal elimination half-life was prolonged in Group 3 (18.6 +/- 5.7 hr) compared with Groups 1 (9.3 +/- 2.3 hr) and 2 (9.7 +/- 1.7 hr), P less than .05. Steady-state volume of distribution ranged from 0.80 to 1.26 L/kg but did not differ among the groups. Total body clearance (CLp) and renal clearance were significantly lower in Groups 2 and 3 patients compared with Group 1 patients. Nonrenal clearance was not related to CLCR. The CLp correlated well with CLCR (CLp = 1.59 CLCR + 33.8, r = 0.830, P less than .05). These data indicate that dosage adjustment may be necessary in patients who have renal insufficiency.

Single bedtime dose of famotidine: assessment of its antisecretory action by 24-hour intragastric pH monitoring

The antisecretory efficacy of a single bedtime dose of famotidine, a new potent H2-receptor antagonist, was evaluated by means of continuous 24-hour intragastric pH monitoring. Of 20 patients with duodenal ulcers, ten randomly received famotidine 40 mg at 10 PM and ten were monitored without medication for control. Famotidine regimen led to a remarkable reduction of gastric acidity in patients who were treated for duodenal ulcer and the drug-induced pH levels were significantly different (P less than .0001) from those of untreated controls. The antisecretory action lasted for 12 hours, which comprised the nocturnal period, whereas no important difference was found between the two groups for the most part of the daytime. The drug was able to keep intragastric pH above 4 units during almost 50% of the whole 24-hour period. These results confirm that famotidine is a powerful and long-acting H2 blocker that relieves gastric acidity during the night and morning hours when administered as a single bedtime dose of 40 mg.

Effects of antacids and food on absorption of famotidine

The effect of a high potency antacid and food on the bioavailability of famotidine was studied in 17 healthy volunteers in an open randomized three-way cross-over trial. After an overnight fast, famotidine was administered to each subject as follows: 40 mg famotidine orally alone; 40 mg orally with antacid; and 40 mg orally with a standard breakfast. Coadministration of the antacid caused a small but significant reduction in the maximum plasma concentration (Cmax) of famotidine from 81.1 +/- 54.2 to 60.8 +/- 21.6 ng ml-1 (P less than 0.05) and a small decrease in the area under plasma concentration-time curve [AUC] from 443.3 +/- 249.2 to 355.0 +/- 125.1 ng ml-1 h (P greater than 0.05). However, there was only a minimal effect of food on these parameters; the Cmax and [AUC] were 81.6 +/- 29.6 ng ml-1 and 434.8 +/- 145.9 ng ml-1 h, respectively.

The effect of famotidine on renal function in patients with renal insufficiency

The effect of famotidine, a new histamine H2-receptor antagonist, on renal tubular creatinine secretion was evaluated in twelve patients with reduced renal function (creatinine clearance 10-60 ml min-1). Creatinine and inulin clearances were determined at baseline and for 4 h after a 10 mg intravenous dose of famotidine. Famotidine renal clearance exceeded inulin clearance by an average of 152%, indicating that renal tubular secretion of famotidine occurred. No significant changes in the clearances of creatinine or inulin, or the fractional clearance of creatinine were observed after famotidine administration. These data suggest that famotidine, unlike cimetidine, does not inhibit renal tubular secretion of creatinine. Thus, famotidine does not affect creatinine-dependent measurements of renal function and is unlikely to alter the renal elimination of basic drugs.

Antisecretory and antiulcer effect of the H2-receptor antagonist famotidine in the rat: comparison with ranitidine

1 The effects of the new H2-receptor antagonist famotidine, administered orally, on gastric secretion and emptying as well as on experimentally-induced gastric and duodenal ulcers were studied in the rat. Ranitidine was used as a reference compound. 2 Both compounds inhibited acid secretion in a dose-dependent manner. Calculated ED50 values were 0.80 and 6.84 mg kg-1 for famotidine and ranitidine, respectively. However, the duration of the antisecretory action was the same for both drugs. 3 The effect of the two drugs, administered at equiactive antisecretory doses, on gastric emptying was different. Ranitidine significantly accelerated the emptying rate whereas famotidine had no effect. 4 Famotidine reduced, in a dose-dependent manner, ulcer incidence in stomachs of dimaprit-treated rats and in duodena of cysteamine-treated animals with a potency respectively 2 and 7 times higher than that of ranitidine. 5 Famotidine is therefore an effective antisecretory and untiulcer compound. Its potency, but not its efficacy, is higher than that of ranitidine. Moreover, the duration of the antisecretory action is virtually the same for both drugs.

The effect of various dose regimens of famotidine on basal nocturnal and meal-stimulated gastric secretion

The antisecretory profile of the H2-receptor antagonist famotidine was studied with various oral doses and regimens in 10 healthy volunteers with high basal acid output (greater than or equal to 5 mEq/hr). Doses included 10, 20, and 40 mg at 9 PM and 9 AM and also 40 mg at 9 PM only. In the 22 hours after the PM doses, overnight (midnight to 7 AM) basal acid secretion was evaluated. Daytime meal-stimulated secretion was assessed at 7 AM, 12 noon, and 5 PM. Doses of 10, 20, and 40 mg inhibited fasting nocturnal basal secretion by 69%, 86%, and 83% to 94%, respectively (P less than 0.01). Meal-stimulated secretion at 7 AM (10 hours after administration) was inhibited by 28% and 39% (P less than 0.01) by only the 40 mg doses. The response to the 12 noon meal was inhibited by the 9 AM doses of 10, 20, and 40 mg by 45%, 75%, and 85%, respectively (P less than 0.01). The effect of a 40 mg dose given at 9 PM only had dissipated by breakfast (7 AM). The response to the 5 PM meal was suppressed by the 20 and 40 mg doses given at 9 AM by 22% and 35%, respectively (P less than 0.05). Suppression was present in only eight of the subjects after the 20 mg dose but in all 10 after the 40 mg dose. The effect on basal gastric aspirate pH values paralleled those seen on acid output. An association was found between mean plasma concentrations of famotidine and mean inhibition of meal-stimulated acid secretion. However, individual values may not be predictive.

Pharmacokinetics of famotidine in man

Famotidine (F) is an effective new H2-receptor antagonist. Knowledge of its pharmacokinetic properties and metabolism is scanty. Therefore, we investigated the disposition of F in 6 healthy male volunteers following a single oral (40 mg) and intravenous (20 mg) dose. F and a metabolite were monitored in plasma or urine by a HPLC method. After intravenous administration plasma levels declined biexponentially with an initial half-life (t1/2) of 0.5 h and a terminal t1/2 of 4.0 h. F was slightly bound to plasma proteins (less than 1 to 15%) and its distribution volume averaged 1.13 l/kg. About 72% of the dose could be recovered as unchanged F in urine. Thus, hepatic clearance contributes to the total plasma Cl of 309 ml/min only 88 ml/min. Consequently, a high hepatic first-pass effect can be excluded. Following oral administration maximum plasma concentrations of 104 +/- 39 ng/ml (mean +/- SD) were observed after 2.3 +/- 1 h. F was eliminated with a t1/2 of 3.6 +/- 1.1 h and its absolute bioavailability ranged from 20 to 66%. In urine an oxidized metabolite could be identified which accounts to about 2% of the given dose. In conclusion, F is rapidly eliminated mainly by the renal route and its t1/2 is slightly longer than those of other available H2-receptor antagonists.

Comparison of famotidine 40 mg with ranitidine 300 mg at night in short-term duodenal ulcer healing. A South African multicentre study

One hundred and thirty-two patients with endoscopically confirmed duodenal ulcers were entered into a 4-6-week double-blind trial of famotidine (Fm) and ranitidine (Rn). Seventy patients were randomised to Fm 40 mg at night and Rn placebo and 62 to Rn 300 mg at night and Fm placebo. Gelusil tablets were allowed for ulcer pain, and diary cards were issued. Clinical evaluations were carried out on entry and at 2 and 4 weeks, and endoscopy was repeated at 4 weeks. Patients with an unhealed ulcer at 4 weeks were continued on the same treatment for another 2 weeks and further endoscopy was carried out at 6 weeks. The groups were comparable with respect to age, sex, duration of the most recent attack, initial ulcer size and smoking, but the duration of disease tended to be longer in the Rn-treated group (P less than 0.05). Of the patients available for analysis, 75% of the Fm-treated and 78% of the Rn-treated patients were healed at 4 weeks and 91% of patients in both treatment groups were healed at 6 weeks. Gelusil consumption and symptomatic responses were comparable in the two groups, and no side-effects were noted apart from mild dizziness in 1 patient after a single Fm tablet. The mean initial size of ulcers healed at 4 weeks was significantly less than that of ulcers which were unhealed at 4 weeks (P less than 0.01), and the healing rate among smokers was significantly lower than that among non-smokers--48 of 72 patients (67%) and 41 of 45 (91%) respectively (P less than 0.01). The study shows that Fm 40 mg at night is as effective as Rn 300 mg in duodenal ulcer healing.

Effect of H2-receptor blockade on gastric mucus composition. A comparative study with ranitidine and famotidine

The effects on gastric mucus by two different H2-receptor antagonists, famotidine and ranitidine, have been investigated in 20 patients with duodenal ulcer. Before and after 4 weeks' treatment with either drug the quality of mucus secretion was assessed by means of a 'mucoprotective index'. A significant (P less than 0.01) decrease in the values of this index was observed in famotidine-treated subjects, whereas no changes were detected in those given ranitidine. The findings of this study with famotidine are in keeping with the results previously reported with cimetidine using the same method. It is suggested that blockade of gastric H2-receptors alters the composition of gastric mucus in man. This effect is not shared by ranitidine.

Clinical pharmacology of famotidine: a summary

Famotidine is a competitive histamine H2-receptor antagonist. Its main pharmacodynamic effect in humans is inhibition of gastric acid secretion. Dose-related suppression of basal and stimulated (meal, pentagastrin) gastric acid output has been shown with oral doses of 5-40 mg. The 40 mg dose is associated with the highest inhibitory effect, the longest duration of action, and the greatest response uniformity. After oral administration, antisecretory activity begins within 1 h, reaches a maximum in 1-3 h, and lasts 10-12 h. In addition to the earlier onset of effect, intravenous famotidine is about twice as potent as oral, a result consistent with a systemic bioavailability of oral famotidine of about 43%. Studies in patients and in healthy volunteers have shown that famotidine does not affect cardiovascular, renal, endocrine, pancreatic exocrine, or gastrointestinal motility functions. Oral famotidine is incompletely absorbed, reaching peak plasma concentrations in 1-3 h. It is eliminated primarily through the kidneys (about 70%), mostly as the parent compound. Its average elimination half-life in healthy subjects is 2.8 h. Half-life is prolonged nonlinearly in patients with decreased renal function. To date, clinically important interactions with other drugs have not been described for famotidine.

Effect of histamine H2-receptor antagonists on DNA synthesis in adult rat hepatocytes in primary culture. Cimetidine enhanced hepatocytes proliferation stimulated with insulin and epidermal growth factor

The effects of three of the most widely used histamine H2-receptor antagonists, cimetidine, ranitidine and famotidine, on liver cell growth were studied in vitro using adult rat hepatocytes in primary culture, because these antagonists are commonly given to patients with hepatic cirrhosis or fulminant hepatic failure for protection against peptic ulcers and gastrointestinal hemorrhage. At their clinically effective concentrations in the blood (0.5-5 micrograms/ml cimetidine, 0.25-2.5 micrograms/ml ranitidine and 0.05-0.5 microgram/ml famotidine), these three antagonists did not have any effect on replicative DNA synthesis either in the presence or absence of insulin plus epidermal growth factor (EGF). However, unexpectedly DNA synthesis stimulated by insulin and EGF was found to be enhanced by 0.05-0.5 mg/ml cimetidine, although it was unaffected or inhibited by ranitidine and famotidine at the concentrations tested. Cimetidine caused maximal enhancement of 1.5-2 times the control level of DNA synthesis at a concentration of 0.25 mg/ml. Cimetidine also had an enhancing effect at submaximal concentrations of insulin and EGF, but neither cimetidine nor the other antagonists had any stimulatory effect on DNA synthesis in the absence of insulin plus EGF. This enhancement of DNA synthesis by cimetidine resulted in significant increase in the total DNA content of the hepatocytes in culture. Under the conditions used, cimetidine had the lowest toxicity of these three antagonists and ranitidine the highest, as judged from data on DNA synthesis and the total protein content of cultured hepatocytes, leakage of aminotransferases from the cells and morphological observations.

Famotidine once-a-day in the therapy of acute, benign gastric ulcer: a worldwide experience

Three hundred thirty-six patients with endoscopically diagnosed benign gastric ulcers, randomly allocated to treatment with 40 mg famotidine at night or placebo, were evaluated in a double-blind multicenter trial conducted in 14 countries worldwide. After 4 weeks, 294 patients qualified for a "per protocol" analysis. Complete ulcer healing was observed in 70 of 149 patients (47%) treated with famotidine 40 mg at night and in 45 of 145 patients (31%) receiving placebo. Cumulative healing rates at 6 weeks were 65 and 46%, and at 8 weeks 80 and 54%, respectively. There were statistically significant differences between the healing rates at each time point (p less than 0.01). The famotidine treatment was significantly more effective at rapidly reducing the incidence of ulcer-related symptoms. Adverse side effects reported were minor and equally distributed between the two groups. The results of this trial show that 40 mg famotidine administered at night is significantly superior to placebo in both accelerating the healing of benign gastric ulcers and in relieving ulcer symptoms. Since 40 mg famotidine administered at night suppresses exclusively nocturnal acid secretion, these findings support the hypothesis that this factor is also of particular importance in the pathogenesis of gastric ulcers.

Terfenadine (single or associated) treatment of adverse reactions to foods

Six groups of patients (total 105), affected by cutaneous signs and symptoms related to food ingestion were studied with regards to the clinical efficacy of some pharmacologic treatments: blind placebo, terfenadine alone, terfenadine associated with pirenzepine or rosaprostol or ranitidine or famotidine. Pharmacologic treatment by terfenadine alone showed poor clinical results, similar to placebo, while the associations of terfenadine with both cytoprotective drugs and anti-H2 receptor antagonists revealed significant clinical improvement which is more evident in those patients treated with cytoprotective drugs combination than those who were treated with anti-H2 antagonists.

Review of an extensive worldwide study of a new H2-receptor antagonist, famotidine, as compared to ranitidine in the treatment of acute duodenal ulcer

The efficacy and safety of famotidine, a new potent H2-receptor antagonist, has been studied in 1,031 patients by 68 investigators in 19 countries in a worldwide dose-ranging multicenter comparative study. Three doses of famotidine (40 mg h.s., 20 mg b.i.d., 40 mg b.i.d.) were compared to ranitidine 150 mg b.i.d. There were no significant differences between the groups in baseline characteristics, including duodenal ulcer size. Efficacy parameters included daytime and nocturnal symptom relief and duodenal ulcer healing, documented by endoscopy, and defined as complete re-epithelialization of the ulcer crater. Significant reductions from baseline for day and night pain, beginning during the first 24 h period, were found in all four treatment groups (p less than 0.01). There was little difference among the four treatment groups with respect to the percentage of patients healed after 4 and 8 weeks of treatment. Healing rates for the three famotidine groups (40 mg h.s., 20 mg b.i.d., 40 mg b.i.d.) were 88, 92 and 92%, respectively, after 8 weeks of treatment as compared to 91% for the ranitidine group. The occurrence and type of adverse clinical experiences reported was similar for each of the four treatment groups. The most common adverse experiences were headache and diarrhea. The results of this study demonstrate that an h.s. dose of famotidine is equivalent to both b.i.d. famotidine and b.i.d. ranitidine in duodenal ulcer healing and pain relief. In view of possible increased patient compliance with a simplified dosage regimen, famotidine 40 mg h.s. is recommended in the acute treatment of duodenal ulcer.

Famotidine: effective treatment of Zollinger-Ellison syndrome

The ability of famotidine to control gastric acid hypersecretion in 32 patients with Zollinger-Ellison syndrome was compared to that of cimetidine or ranitidine. Equipotent doses of each drug were determined in nine patients and famotidine was nine times more potent than ranitidine and 32 times as potent as cimetidine. Famotidine had a 30% longer duration of action than either ranitidine or cimetidine. The 32 patients were treated with famotidine for a mean follow-up of 10.5 months. No hematologic, biochemical, or clinical toxicity occurred. Famotidine appears to be the histamine H2-receptor antagonist of choice in the treatment of Zollinger-Ellison syndrome.

Famotidine. The ACG Committee on FDA-Related Matters with primary authorship by G. Friedman. American College of Gastroenterology

Famotidine is a potent H2 receptor antagonist containing a thiazole ring structure, thus differing chemically from cimetidine and ranitidine. Pharmacologically, famotidine is nine times more potent than ranitidine and 32 times more potent than cimetidine. In the Zollinger-Ellison syndrome famotidine is more potent than cimetidine or ranitidine and has a 30% longer duration of action. Randomized double-blind controlled duodenal ulcer studies reveal famotidine effectively heals active ulcers when compared to placebo and that healing rates are comparable to those seen at 8 wk with ranitidine. Famotidine effectively heals gastric ulcers in 8 wk when compared to placebo. The drug also significantly reduced the recurrence rate of duodenal ulcers in a 6-month controlled trial. Famotidine is a potent H2 antagonist which appears to be safe at high doses, does not cause antiandrogen side effects, and does not interfere with hepatic oxidative metabolism. Further clinical experience will define famotidine's place in the therapeutic armamentarium against peptic ulcer disease.

Effect of histamine and its blockers on plasma beta-endorphin-like immunoreactivity in rats

The effect of histamine and related compounds on the plasma beta-endorphin-like immunoreactivity (beta-En-Li) levels in rats were studied. Histamine (2.5 mg/kg), mepyramine (10 mg/kg) or famotidine (5.0 mg/kg) was injected i.p., and the animals were serially decapitated. The plasma beta-En-Li levels were measured by radioimmunoassay. Effects of histamine, mepyramine and famotidine on beta-En-LI release from the anterior pituitary were also investigated by means of an in vitro experiment. The beta-En-LI content in the hypothalamus and pituitary gland did not change significantly after histamine, mepyramine and famotidine injection. The plasma beta-En-LI levels increased significantly in a dose-related manner with a zenith at 20 min after histamine injection and decreased significantly after mepyramine injection, but did not change significantly after famotidine injection. Effects of histamine on plasma beta-En-LI levels were prevented with the pretreatment of mepyramine. The beta-En-LI release from the anterior pituitary was enhanced with the addition of histamine to the medium, and histamine's effects were blocked with an addition of mepyramine to the medium. These findings suggest that histamine acts as to stimulate beta-En-LI release from the anterior pituitary, and that histamine's effects may be mediated via H1-receptor.

Effect of famotidine on hepatic hemodynamics and peptic ulcer

The acute effects of histamine H2 receptor antagonist, famotidine, on hepatic hemodynamics were studied in six normal volunteers and eight patients with chronic liver disease, and its chronic effects on peptic ulcer, portal hemodynamics, and hepatic function were studied in 20 patients with chronic liver disease and peptic ulcer (16 with gastric ulcer, four with duodenal ulcer). Infusion of 20 mg famotidine did not reduce hepatic blood flow and portal blood flow in normal subjects, nor did it reduce cardiac output, the gradient between wedged hepatic vein pressure and free hepatic vein pressure, hepatic blood flow, and portal blood flow in patients with chronic liver disease. An oral dose of 20 mg famotidine twice daily for 2 months healed peptic ulcer in 19 of 20 patients (95%) with chronic liver disease and peptic ulcer, without any change in portal blood flow and hepatic function. Thus famotidine does not appear to alter hepatic hemodynamics and hepatic function in normal subjects and patients with chronic liver disease.

Pharmacological management of patients with peptic ulcer disease: prospects for the late 1980's

Over the past ten years there have been major advances in the physician's ability to treat patients with peptic ulcer disease. Cimetidine continues to be the standard against which newer therapies are generally compared, although ranitidine is equally effective for short-term therapy, more effective for maintenance therapy, and has a superior safety profile. Famotidine is an even more potent H2 receptor antagonist, and initial clinical studies are promising. The initial concern for the development of gastric carcinoid lesions in rodents, maintained for long periods on high doses of omeprazole, defused the initial enthusiasm for this hydrogen-potassium ATPase "proton pump" inhibitor, but recent studies continue to show a marked efficacy of this agent for the short-term care of patients with gastric or duodenal ulcers and for the management of patients with the Zollinger-Ellison syndrome. Sulcrate continues to enjoy wide popularity for acute and chronic care of acid peptic disorders because of its local action and minimal adverse effects. Pirenzepine is effective in achieving and maintaining healing, but prevalence of anticholinergic side-effects has hampered enthusiasm for its widespread use. The 2 forerunners in the prostaglandin analogues arena, misoprostol and enprostil, are antisecretory agents when given in sufficiently high doses. These orally administered prostaglandins have a favourable safety profile, and their only adverse effect is that of the development of transient mild diarrhea. Finally, while antacids continue to be used in large amounts because of their over-the-counter availability, their clinical usefulness is limited by their unpalatable taste and the relatively large amounts usually required to achieve ulcer healing.