Effect of cimetidine, ranitidine, famotidine and omeprazole on hepatocyte proliferation in vitro

Recently reports have indicated that both cimetidine and ranitidine delay cell proliferation in rats following 70% partial hepatectomy and result in an increased mortality following this procedure. The present study was designed to determine whether three H2 blocking agents (cimetidine, ranitidine, famotidine) and a new, powerful antisecretory drug (omeprazole) specifically influence hepatocyte proliferation in primary culture. Hepatocytes were isolated from livers of normal male rats by the standard collagenase perfusion technique. Hepatic DNA synthesis and percent of labelled nuclei were determined after 48 h incubation. Hepatocytes in culture were incubated with the H2 blocking agents and omeprazole or with different concentrations of serum obtained from sham-operated or 70% hepatectomized rats treated or not with the same agents. Rats were injected intraperitoneally at 8:00 a.m. on two consecutive days. In hepatectomized rats, the first dose was injected at 8:00 a.m. immediately after surgery, the second, 24 h later. The serum of sham-operated or 70% hepatectomized rats that did not receive drugs served as control. No changes in DNA synthesis, percentage of labelled nuclei and transaminase were detected when the agents were added to the hepatocytes in culture at concentrations within the effective pharmacological dosage and 30 times higher. Similarly, no changes in these parameters were obtained when different concentrations of serum obtained from sham-operated rats treated with H2 blocking agents or omeprazole were added to the basal culture medium. However, a significant inhibition of DNA synthesis and of percentage of labelled nuclei was observed when hepatocytes were incubated in the presence of serum from 70% hepatectomized rats that had been treated with cimetidine or with ranitidine. The serum of 70% hepatectomized rats treated with famotidine and omeprazole had no effect on hepatocyte proliferation in vitro. No effect on transaminase was found in these conditions.

Pharmacokinetics of famotidine in elderly patients with and without renal insufficiency and in healthy young volunteers

The pharmacokinetics of the H2-receptor antagonist famotidine, after oral administration of a 20 mg tablet, has been studied in 10 elderly patients with normal renal function (CLCR greater than or equal to 59 ml.min-1, Mean = 80 ml.min-1), 5 elderly patients with renal insufficiency (CLCR less than or equal to 38 ml.min-1, Mean = 15 ml.min-1), and 6 healthy young volunteers. Elimination half-life in the elderly patients with renal insufficiency was significantly prolonged compared to the elderly patients with normal renal function and the young volunteers. The correlation coefficient between creatinine clearance and the elimination rate constant of famotidine was 0.672. Mean urinary recovery of unchanged drug up to 24 h in the young volunteers was 44%. The mean renal clearance of famotidine in the young volunteers (270 ml.min-1) was substantially greater than the creatinine clearance, 128 ml.min-1, which suggests the possibility of tubular secretion of famotidine.

[Treatment of duodenal ulcer with famotidine. (Multicenter study)]

A multicenter open study aimed at evaluating the effect of famotidine in the treatment of duodenal ulcer was performed in several institutions located in 15 different cities of Mexico. One-hundred-and-fourteen patients with duodenal ulcer demonstrated by endoscopy were given 40 mg. of famotidine daily, administered as a single dose at night. After 4 and 6 weeks of treatment, healing of the ulcer was observed in 81.6% and 95.6% of patients, respectively. Side-effects were very unusual. In only one patient, who experienced vertigo during the treatment, administration of the drug had to be stopped.

A comparison of the influence of famotidine and cimetidine on phenytoin elimination and hepatic blood flow

The H2-receptor antagonist cimetidine has been reported to decrease the hepatic clearance of numerous drugs by inhibiting cytochrome P-450 metabolism, decreasing liver blood flow or both. In this open-label, randomized crossover study we determined whether therapeutic doses of famotidine, a newer H2-receptor antagonist, has similar effects. Ten healthy subjects received single doses of both phenytoin 100 mg orally and indocyanine green intravenously without other treatment, and then again during treatment with famotidine or cimetidine. After a drug-free period, this sequence was repeated with the alternate H2-receptor antagonist. Cimetidine decreased the plasma clearance of phenytoin by 16% +/- 14% (mean +/- s.d.), but was not found to have a significant influence on phenytoin volume of distribution or terminal elimination rate constant nor on blood clearance of indocyanine green. Famotidine was not found to alter either phenytoin or indocyanine green kinetics.

A multicenter, randomized, double-blind study comparing a daily bedtime administration of famotidine and ranitidine in short-term treatment of active duodenal ulcer

The efficacy and safety of famotidine and ranitidine in the treatment of active duodenal ulcer were compared in a multicenter, randomized double-blind study. The study was carried out in 5 centers which included a total of 143 patients with endoscopically documented active duodenal ulcer. The patients received either famotidine (1 tablet of 40 mg at night) or ranitidine (2 tablets of 150 mg at night). Endoscopic examinations were performed at 4 and 6 weeks of active treatment. Day and nocturnal pain were also monitored and the laboratory and clinical profiles evaluated. One hundred and thirty-three patients fulfilled the evaluation criteria (66 patients in the famotidine group and 67 in the ranitidine group). Healing rates at weeks 4 or 6 of treatment showed no significant differences between the famotidine and the ranitidine groups. The healing rates were 79% at week 4 and 96% at week 6 in the famotidine group, and 77% at week 4 and 95% at week 6 in the ranitidine group. Similar results were observed in both treatment groups with regard to pain resolution, decrease in antacid intake and safety profile.

[Negative inotropic action of famotidine]

In a randomized placebo-controlled study, 12 healthy volunteers were treated for one week each with nifedipine 10 mg four times daily or the same dose of nifedipine concurrently with famotidine 40 mg once daily per os. Famotidine did not significantly alter pharmacokinetic parameters of nifedipine. Determination of systolic time intervals showed that pre-ejection period (PEPc) and the ratio of pre-ejection period over left ventricular ejection time (PEP/LVET) were significantly reduced by administration of nifedipine plus placebo. Coadministration of famotidine and nifedipine, however, led to a significant increase in these parameters. Also, administration of famotidine alone to the same subjects led to a significant rise in PEPc and PEP/LVET. In impedance cardiography, stroke volume and cardiac output were significantly reduced by famotidine, whereas the H2-antagonist did not alter heart rate. This observation indicates for the first time that famotidine may exert negative effects on cardiac performance. In our opinion this could be of clinical relevance in elderly subjects or in patients with heart failure.

Famotidine-associated mental confusion in elderly patients

Central nervous system effects, such as mental confusion and hallucinations, have been reported with both cimetidine and ranitidine. Elderly patients with renal or hepatic dysfunction are more susceptible to these adverse reactions. We report two cases of reversible mental confusion in elderly patients with mild renal insufficiency following intravenous famotidine therapy, possibly explained by an increased permeability of the blood-brain barrier in patients with decreased renal function.

Prophylaxis against acid aspiration syndrome. Single oral dose of H2-antagonist on the evening before elective surgery

We have compared famotidine 40 mg, ranitidine 300 mg and placebo given in a single oral dose at 2200 hours as the sole means of prophylaxis in 286 patients who underwent elective surgery the following day. Standardised premedication was administered and anaesthesia induced. Gastric contents were aspirated by nasogastric suction and the pH and volume measured. Median values of pH after famotidine, ranitidine and placebo were 6.17, 6.74 and 2.45 respectively; median aspirate volumes were 8, 8 and 10 ml respectively. The proportions of patients considered 'not at risk' (pH greater than 2.5) were 90% after famotidine, 91% after ranitidine and 52% after placebo. We conclude that the administration of a potent H2-antagonist in a single oral dose at night offers a convenient routine means of providing extensive prophylactic cover in patients scheduled to undergo elective surgery the following day.

Further evidence that brain histamine H2 receptors are stimulatory in the control of prolactin in the rat

The effects of administration into the brain ventricle of H2 receptor agonists (4-methylhistamine, 0.8 mumol/rat; dimaprit, 0.4-0.8 mumol/rat), H2 antagonists (cimetidine, 0.8 mumol/rat; ranitidine, 0.4-0.8 mumol/rat; famotidine, 0.03 mumol/rat) and of the dimaprit chemical analogue SK&F 91487 (0.4 mumol/rat) on unstimulated and histamine-stimulated prolactin secretion in normal male rats were studied. The H2 agonist 4-methylhistamine caused a significant increase in unstimulated blood PRL, whereas dimaprit, SK&F 91487, and the H2 antagonists tested did not change PRL levels. 4-Methylhistamine significantly enhanced the stimulatory effects of histamine on prolactin, whereas all the H2 antagonists inhibited histamine-induced prolactin release. The inhibition of histamine-induced prolactin secretion by the H2 agonist dimaprit is nonspecific, since its chemical analogue SK&F 91487, which has no H2 agonist activity, also inhibits it. These results indicate that stimulation of the H2 receptors in the central nervous system is facilitatory for PRL secretion, suggesting that the activation of H2 receptors may contribute to the PRL-releasing effects of histamine.

Do anticholinergics interact with histamine H2 receptor antagonists on night intragastric acidity in active duodenal ulcer patients?

The effect of administering low doses of famotidine or ranitidine alone or in combination with an M1-receptor-selective antagonist, pirenzepine, on night intragastric acidity was evaluated in 16 active duodenal ulcer patients to verify 1) whether anticholinergics and H2-antagonists have a synergic effect on inhibition of night gastric acidity, and 2) whether patients with vagal hypertone are more sensitive to anticholinergics than the remainder of the duodenal ulcer population. The endogastric pH was continuously recorded for 12 h (8 PM-8 AM) after random, single-blind administration of one of the following drug regimens: 20 mg famotidine, 150 mg ranitidine, 50 mg pirenzepine, 20 mg famotidine plus 50 mg pirenzepine, and 150 mg ranitidine plus 50 mg pirenzepine. Six patients with a basal acid output:peak acid output BAO:PAO greater than 0.3 were considered "vagal hypertone" subjects. Night gastric acidity inhibition was -39.6% with pirenzepine (p less than 0.001) and -73.7% and -71.5% with famotidine or ranitidine (p less than 0.001 vs. pirenzepine). The simultaneous administration of pirenzepine with famotidine or ranitidine provoked only a slight, insignificant increase in percent suppression, 5.1% and 6.3%, respectively, and did not modify either the time lag to onset of anti-H2 action or the duration of action. Patients with a BAO:PAO greater than 0.3 were not more sensitive to anticholinergic treatment than other duodenal ulcer patients. Our study furnishes evidence that combined administration of anti-H2 and anticholinergics is not significantly better than anti-H2 alone, in active duodenal ulcer patients.

Plasma famotidine concentration versus intragastric pH in patients with upper gastrointestinal bleeding and in healthy subjects

To study the concentration-response relationship of famotidine, we serially monitored intragastric pH and measured plasma drug concentrations simultaneously after an intravenous injection of this H2-receptor antagonist (0.1 mg/kg) in eight patients with upper gastrointestinal bleeding and in six healthy subjects. By applying the sigmoidal Emax model the mean (+/- SD) plasma famotidine concentrations associated with an intragastric pH of 4.0 in patients and healthy subjects were estimated to be 17.7 +/- 10.7 and 24.8 +/- 10.3 ng/ml, respectively (not significantly different). No significant differences were observed in the mean pharmacokinetic parameters between the two study groups. Multiple regression analysis revealed that not only a pharmacokinetic factor (i.e., elimination t1/2) but also a pharmacodynamic (or sensitivity) factor (i.e., a drug concentration associated with an intragastric pH of 4.0) contributed significantly (p less than 0.01) to the overall variability in the duration of antisecretory effect in our study subjects, with standardized partial regression coefficients of 0.54 and -0.63, respectively. Based on these data, we predict that around-the-clock control of a fasting intragastric pH above 4.0 can be attained by a continuous infusion of famotidine at rates ranging from 6 to 25 mg/day (mean +/- SD, 11 +/- 7 mg/day) in a 70 kg patient whose pharmacokinetic and pharmacodynamic characteristics are similar to those of our patients.

Effect of H2 antagonists cimetidine and famotidine on the hemotoxicity of cyclophosphamide

A comparison between the effects of H2 antagonists Cimetidine and Famotidine on the hemotoxicity of Cyclophosphamide in vivo in DBA/2NCrBl mice is described. Hemotoxicity of anticancer drug was determined by peripheral blood leukocytes, bone marrow cells and bone marrow CFU-S, GM-CFC. Results show that Famotidine does not increase Cyclophosphamide hemotoxicity while Cimetidine enhances the toxicity of the anticancer drug only on normal pluripotent hemopoietic stem cells.

Chemical stabilities of famotidine and ranitidine hydrochloride in intravenous admixtures

The chemical stabilities of famotidine and ranitidine hydrochloride solutions in 5% dextrose and 0.9% sodium chloride injections have been studied using high-performance liquid chromatographic methods (HPLC). Both the drugs were stable for at least 15 days (loss in potency of less than 10%) at 25 degrees C and 63 days at 5 degrees C. Both drugs were comparatively less stable in 5% dextrose injection than in 0.9% sodium chloride injection. The loss in the potency of phenol, which is added as a preservative to ranitidine hydrochloride injection, was significant in both the vehicles. However, the addition of preservative in a single dose vial is not considered necessary.

Famotidine effects on theophylline pharmacokinetics in subjects affected by COPD. Comparison with cimetidine and placebo

The effect of a new H2-antagonist, famotidine, on theophylline pharmacokinetics was compared with placebo and cimetidine in 26 patients affected by COPD. Cimetidine, placebo, and famotidine were administered, four days each drug at random, to all the subjects. Results suggest that famotidine, contrary to cimetidine, does not influence theophylline metabolism in man.

Pharmacokinetics and dynamics of famotidine in patients with renal failure

1. Famotidine, a new histamine H2-receptor antagonist was administered intravenously (20 mg) to 22 patients with end stage renal disease during a dialysis free interval (n = 6) and during different blood purification processes including haemodialysis (HD; n = 4), intermittent haemofiltration (HF; n = 4), continuous haemofiltration (CHF; n = 4) and continuous ambulatory peritoneal dialysis (CAPD; n = 4). The plasma, the dialysate/filtrate and the urine concentrations of famotidine were analysed by h.p.l.c. 2. In addition, intra-gastric pH was measured by a long-term-pH probe in seven patients with renal failure and in six patients with normal renal function (control group) following 20 mg famotidine. 3. A 7 to 10 fold prolongation of famotidine's elimination half-life (27.2 +/- 8.5 h; mean +/- s.d.) was observed in patients with renal failure as compared with the half-life (2.6-3.6 h) in subjects with normal renal function. 4. Total body clearance (CL) and volume of distribution (V) were found to be 33.5 +/- 10.1 ml min-1 and 1.3 +/- 0.7 l kg-1, respectively in patients with end-stage renal failure. 5. Blood purification processes have shown considerable variation in clearing famotidine from the body: 16.4 +/- 8.9 and 6.0 +/- 2.9% of the administered dose in HD with polysulphone and cuprophan membranes respectively, 7.7 +/- 5.2% in HF with a polyacrylonitrile membrane (each for 5 h), 4.5 +/- 1.1% in CAPD and 16.2 +/- 4.9% in CHF with a polysulphone membrane within 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Overnight comparable anacidity by standard large and half-single bedtime doses of H2 antagonists in duodenal ulcer patients: a clinical pharmacological study

We continuously monitored 24-h intragastric pH in eight ulcer patients--who received orally at 10 PM in double-blind, randomized fashion either placebo, ranitidine 150 mg and 300 mg, or famotidine 20 mg and 40 mg, on five separate occasions--in order to determine whether half the commonly used bedtime doses of the H2 antagonists would suppress overnight acidity to the same extent as the large doses. Our results show that, during the nocturnal period (from 11 PM to 8 AM), significantly higher pH values were obtained with the large doses than with the half doses of both ranitidine (p = 0.00005) and famotidine (p = 0.00004). However, hydrogen ion activity was virtually nil with each H2 blocker dose regimen, and the percent inhibition of acidity over placebo was 100% for all of them (p = approximately equal to 0). Further more, with regard to the nocturnal period elapsed in min above 5.0 pH units, there was no significant difference between the two ranitidine doses (p = 0.39) and the two famotidine doses (p = 0.81). Therefore, the two dosing schedules of each H2 antagonist increased intragastric pH differently, but both the half and the standard large regimens produced similar overnight virtual anacidity. It is suggested that ranitidine and famotidine should be evaluated in the acute treatment of duodenal ulcer, using single bedtime doses half those commonly employed.

[Effects of omeprazole and famotidine on (H+-K+) ATPase and acid secretion in rabbit gastric glands]

Effects of omeprazole, an anti-ulcer drug, on (H+-K+) ATPase activity and gastric acid secretion in a gastric mucosal gland preparation from rabbits were investigated. The mode of action of the substance was compared with famotidine, and H2 antagonist, by examining the effects of both drugs on the (H+-K+) ATPase of the rabbit gastric mucosa and on gastric acid secretion from the isolated rabbit gastric glands. Optimal assay conditions for (H+-K+) ATPase activity differed slightly from that reported for pig gastric mucosa, and they were pH 7.0, 2 mM of MgCl2 and 50 mM of KCl. Omeprazole dose-dependently inhibited the enzyme activity with an IC50 of 4.2 microM, whereas famotidine was not inhibitory even at the highest concentration of 100 microM. Acid secretion in the glands was determined by measuring accumulation of 14C-aminopyrine. Omeprazole and famotidine showed almost the same inhibitory effect against histamine-stimulated gastric secretion, and their IC50 values were 0.35 microM. Omeprazole inhibited dibutyryl cyclic AMP-stimulated gastric acid secretion, but famotidine was not inhibitory even at the highest concentration of 100 microM. The reason for this difference was that (H+-K+) ATPase activity is linked to the final step of acid secretion. From these results, omeprazole can be expected to be useful for the treatment of peptic ulcer disease.

Histamine H2-receptor antagonists

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

Cytoprotective action of roxatidine acetate HCl

The cytoprotective action of roxatidine acetate HCl (roxatidine) was investigated. We also studied the involvement of endogenous prostaglandins (PGs) in the cytoprotective action of roxatidine and the effect of roxatidine on SRS content in pleurisy induced by A23187. Simultaneously, these effects of roxatidine were compared with those of other histamine H2-receptor antagonists at the same anti-secretory activity level. Roxatidine prevented formation of the gastric mucosal lesions induced by abs. ethanol, 0.6 N HCl and 0.2 N NaOH, but it failed to prevent 30% NaCl-induced gastric mucosal lesions. Cimetidine, ranitidine and famotidine failed to prevent formation of the gastric mucosal lesions induced by necrotizing agents. The cytoprotective action of roxatidine was not abolished by pretreatment with indomethacin. Roxatidine did not greatly influence SRS production. Consequently, it appears that roxatidine has a cytoprotective action and that this action is not associated with endogenous PGs and SRS.

Effects of H2-receptor antagonists on ethanol metabolism in Japanese volunteers

The effects of H2-receptor antagonists (cimetidine, ranitidine, and famotidine) on ethanol metabolism were investigated. Neither in aldehyde dehydrogenase (ALDH)-1 deficient subjects nor in those with normal ALDH-1, did the three H2-receptor antagonists and placebo differ in their effects on the pharmacokinetic parameters of ethanol (i.e. peak time (tmax), metabolic rate (k0), peak serum concentration (Cmax), volume of distribution (V) and area under the concentration-time curve (AUC). The AUC of acetaldehyde was slightly but significantly (P less than 0.05) larger only after treatment with cimetidine. Cmax and tmax of acetaldehyde were unchanged.

[Effect of an H+, K+-ATPase inhibitor, omeprazole (OPZ), on gastric acid secretion and gastric or duodenal lesion. Comparison with an H2-receptor antagonist, famotidine (FMD)]

In pylorus ligated rats, OPZ inhibited gastric acid secretion dose-dependently, with a potency greater than that of FMD. At the same time, OPZ increased gastric K+ secretion and inhibited pepsin and Na+ secretions at the highest dose. In Heidenhain pouch dogs, single injection of OPZ inhibited gastric acid secretion induced by histamine to a degree almost equal to that by FMD. In the case of repeated administration, anti-secretory activity of OPZ was enhanced by up to several days and then remained constant. After several days, the inhibitory activity of OPZ was more potent and longer than that of FMD, and it still had not ceased 22hr after administration. In pylorus ligated rats, OPZ prevented gastric ulceration, and the potency was greater than that of FMD. OPZ promoted healing of gastric and duodenal ulcers induced by acetic acid in rats. At the same doses, FMD failed to promote the healing of both ulcers. In water-immersion stressed rats, OPZ prevented formation of gastric erosions, with a potency greater than that of FMD. In addition, OPZ prevented formation of gastric erosions induced by ethanol in rats. These results indicate that the anti-secretory and anti-ulcer activities of OPZ are superior to those of FMD, so that OPZ should have excellent therapeutic application for peptic ulcers.

Once and twice daily doses of H2 antagonists revisited, using continuous intragastric pH monitoring

Eight patients with previous duodenal ulcer in symptomatic remission underwent continuous intraluminal pH monitoring on five separate occasions to compare the effects on 24-h intragastric acidity of placebo, 300 mg ranitidine at night, 150 mg ranitidine twice daily, 40 mg famotidine at night, and 20 mg famotidine twice daily. All H2 blocker treatments were superior to placebo (p congruent to 0), whereas the twice daily doses of both ranitidine and famotidine were significantly better (p congruent to 0 and p = 0.00006, respectively) than the single ones in reducing 24-h intragastric acidity. The higher acid inhibitory effect of the twice daily dose regimens than of the single ones was evident during the daytime, whereas no difference between them was found during the nighttime (from 2200 to 0800 h). These data are at variance with those previously published, and the slight effect of the single nightly doses of H2 blockers on daytime acidity seems to confirm further that the suppression of nocturnal acidity may really be the decisive factor in the success of this dosing schedule in treating duodenal ulcer.

Differential inhibition of human liver phenacetin O-deethylation by histamine and four histamine H2-receptor antagonists

1. The effects of histamine and four histamine H-2 receptor antagonists on phenacetin O-deethylation by microsomal preparations of four human livers was quantified by a radiometric-thin layer chromatographic method. 2. Histamine and three of these drugs, namely cimetidine, ranitidine and famotidine, were weak inhibitors of this cytochrome P-450-catalysed O-deethylation, but mifentidine was a potent competitive inhibitor with a Ki in the range 40-70 microM. 3. Cimetidine, histamine and mifentidine are all 4(5)-substituted imidazole derivatives, and the contrast between the very weak inhibitory effects of cimetidine and histamine, and the more potent effect of mifentidine, suggests that the imidazole moiety may play little role in the inhibition of phenacetin O-deethylase by mifentidine. 4. The demonstration that cimetidine, ranitidine and histamine were all poor inhibitors of phenacetin oxidation further suggests the possible lack of identity between the human liver cytochrome P-450 isoenzymes responsible for catalyzing the oxidation of metoprolol and phenacetin. This follows from recognizing that metoprolol oxidation is known, from both in vivo and in vitro studies, to be strongly inhibited by both of these H-2 receptor antagonists and from in vitro studies also to be inhibited by histamine.

Continuous intravenous infusions of famotidine maintain high intragastric pH in duodenal ulcer

Three double blind crossover studies were carried out to assess the ability of primed infusions of famotidine to raise intragastric pH over 24 hours in 12 duodenal ulcer patients. pH was measured continuously using intragastric electrodes and solid state recording devices. The studies compared the effects of placebo, famotidine 10 mg bolus injection iv followed by continuous infusions of 3.2 mg/h and 4 mg/h in random order. Gastric acidity decreased significantly with both dose regimens (p less than 0.0005) but the effects of either dosage were similar. During fasting median pH rose from 1.35 to 7.1 and 7.05 respectively. During the day, when standard meals were taken, median pH rose from 1.30 to 4.3 and 3.65 respectively. Despite continuous infusions the H2-antagonist was less effective during this time. The latter finding raises questions about gastric secretory control during the day when food is eaten.

Comparison of famotidine with cimetidine and ranitidine

The pharmacodynamic, therapeutic, and toxicologic properties of famotidine are evaluated and compared with those of cimetidine and ranitidine. Famotidine, an H2-receptor antagonist with a thiazole nucleus, is approximately 7.5 times more potent than ranitidine and 20 times more potent than cimetidine on an equimolar basis. Therapeutic trials indicate that famotidine 20 mg b.i.d. or 40 mg at bedtime is as effective as standard doses of cimetidine and ranitidine for healing duodenal ulcers. A dose of 40 mg at bedtime appears to heal benign gastric ulcers. A single nocturnal dose of 20 mg is effective in preventing duodenal ulcer relapse. Further studies are required that compare the efficacy of famotidine with cimetidine and ranitidine in the treatment of gastric ulcers and in the prevention of recurrent duodenal ulcers. The overall incidence of adverse effects observed with famotidine appears to be similar to that reported for cimetidine and ranitidine. Like ranitidine, famotidine does not have antiandrogenic effects or substantially inhibit the hepatic metabolism of drugs. Because of its increased antisecretory potency and lack of antiandrogenic effects at higher doses, famotidine may be the H2-receptor antagonist of choice in treating Zollinger-Ellison syndrome. Additional clinical experience, as well as cost and safety factors, will determine the place of famotidine in treating and preventing acid-peptic disorders.

Pharmacological control of the histamine H2 receptor-adenylate cyclase system by famotidine and ranitidine in normal and cancerous human gastric epithelia

In human fundic glands, famotidine was about 17 times more potent than ranitidine as an inhibitor of histamine - stimulated cAMP generation. This H2-receptor antagonist had no effect on the receptor-adenylate cyclase systems sensitive to PGE2, isoproterenol (beta 2-receptor), VIP and on forskolin-induced activation of the Gs/catalytic units of the membrane-bound enzyme prepared from human fundic glands. In the HGT-1 human gastric cancer cell line, famotidine and ranitidine showed long lasting, irreversible actions probably related to a slow rate of dissociation from the histamine H2-receptor.

A comparative evaluation of the transport of H2-receptor antagonists by the human and baboon placenta

Using a single cotyledon perfusion model, the placental transport of four H2-receptor antagonists, cimetidine, famotidine, nizatidine, and ranitidine, was determined and compared using normal term human and normal preterm baboon placentas. In both the human and baboon placentas, the transport of each agent was similar whether administered singly or in combination with the other drugs. Drug transport was the same in both directions, maternal-to-fetal and vice versa, indicating a lack of preferential transfer. The H2-receptor antagonists were transported at about 40% the rate of the freely diffusable reference compound, antipyrine. There were no significant differences between the human and baboon in any of the parameters of placental function evaluated. Placental glucose and oxygen consumptions, and lactate production were comparable in the human and baboon preparations. The transport and clearance of each of the H2-antagonists were similar in each species.

The effects of famotidine, 40 mg at night, on 24-hour intragastric acidity and plasma gastrin concentration in healthy subjects

The effects of 40 mg oral famotidine at 2115 h on 24-h intragastric acidity and plasma gastrin concentration were measured in a double-blind placebo-controlled study in 10 healthy subjects. The subjects were studied on the 7th day of treatment with either famotidine or placebo. Famotidine, 40 mg at night, caused a pulse of decreased intragastric acidity during the night, with a longer-lasting elevation of plasma gastrin concentration. However, in the latter part of the day there was complete recovery from the antisecretory effects of the drug, with normal intragastric acidity and normal concentrations of plasma gastrin.

Effect of the H2-blocker famotidine on gastric mucosal prostaglandin levels in water immersion stress in rats

A quantitative and rapid method was developed for determination of tissue prostaglandin (PG) levels using reverse phase high performance liquid chromatography. Using this method, we investigated the effects of famotidine (YM-11170), an H2-blocker, on changes in gastric mucosal PG levels induced by water immersion stress in rats. Gastric mucosal phospholipase (PLase) activity was also estimated. Four kinds of PGs, i.e., 6-keto-PGF1a, PGE2, PGF2a, and PGD2 were detected in gastric mucosa. 6 h water immersion stress induced decreases in all of them at a similar degree, the reduction being about 70% of the control value. Decreases in PLase activity were also observed in rats with 6 h stress. Pretreatment with famotidine prevented decreases in levels of PGs, which are known to have cytoprotective effect, and also maintained PLase activity. These results indicate that famotidine exerts its anti-ulcer action via maintenance of PG levels and PLase activity.

Medical management of patients with Zollinger-Ellison syndrome who have had previous gastric surgery: a prospective study

We examined prospectively the criteria for medical management in 16 patients with Zollinger-Ellison syndrome who had had previous gastric surgery. Each patient received sufficient antisecretory medication to lower gastric acid output to less than 10 mEq/h during the last hour before the next dose of drug. The 7 patients with a vagotomy but no gastric resection were symptom-free and had no mucosal disease. Of 9 patients with a partial gastrectomy, 7 had mucosal disease, with or without symptoms, and 6 of the 7 patients had acid outputs of 5-10 mEq/h. In these patients, antisecretory medication was increased to reduce output to less than 5 mEq/h and symptoms and mucosal abnormalities resolved in each patient. Patients with Zollinger-Ellison syndrome and a vagotomy can be treated safely by reducing acid secretion to less than 10 mEq/h, but in patients with a partial gastrectomy, acid secretion must be reduced to less than 5 mEq/h, and adequacy of therapy must be checked further by endoscopy.