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New aspects of clinical pharmacology of antacids.

Most antacids contain magnesium and/or aluminium hydroxide but some include also bicarbonate and calcium carbonate. The net effect of antacid action is the reduction in gastric acidity and in peptic activity but recent studies indicate that aluminium-containing antacids exhibit the cytoprotective activity or enhancement of natural mucosal defense mechanisms. This protective action has been attributed, in part, to the release of endogenous prostaglandins but other mediators such as hexa-aquo-aluminium cation and nitric oxide have also been proposed. Aluminium-containing antacids are known to accelerate the healing of chronic gastroduodenal ulcerations and this has been attributed primarily to their acid neutralizing capacity. Since antacids interact with luminal epidermal growth factor (EGF) which exhibits ulcer healing properties it has been proposed that this peptide is implicated in the healing of gastroduodenal ulcerations by these drugs.

Animals↗

Clinical use of antacids.

Antacids have for long been regarded as the mainstay of pharmacologic therapy in patients with dyspepsia. The advent of the histamine H2-antagonist and of proton pump inhibitors has provided simpler and overall more efficient therapeutic modalities for severe forms of dyspepsia. This relates especially to aggressive forms of peptic ulcer disease and severe reflux oesophagitis, where even high dose histamine H2-antagonist therapy has its clear limitations. Antacids nevertheless continue to be widely used in less severe forms of dyspepsia, especially in patients suffering from heartburn. In such patients self medication of antacids as first therapeutic measure is still very common. This is well exemplified by an American nd British survey. Out of 6760 randomly selected British general practice patients 875 suffered from reflux-like symptomatology without having consulted their physician for the symptomatology for minimum one year. Antacids were taken by 61% of them. The advent of controlled endoscopic trials and the emergence of the H2-receptor blockers as a yardstick of ulcer therapy, however, facilitated reappraisal of the value of antacids in various conditions. This has given a clear-cut answer in well defined entities such as peptic ulcer disease and stress ulcer prophylaxis but has left many open questions in heterogeneous conditions especially in and around gastroesophageal reflux disease.

Antacids↗

[Antacid activity of citrate-bicarbonate complex of effervescent formulations of ranitidine. In vitro analysis using 'artificial stomach-duodenum' model].

Antacid activity supported by citrate-bicarbonate complex of four effervescent ranitidine forms has been assessed in vitro using an 'artificial stomach-duodenum' model controlled by microcomputer. This model allows (i) maintenance of constant the rates of the fluxes throughout the experiments or (ii) simulation of gastroduodenal flux regulation, in the normal subject (NS) or in the duodenal ulcer patient (DU) situation. The four forms developed a theoretical maximal antacid capacity between 61 and 81 mmol with a maximum intragastric pH between 3.2 and 4.8. In the gastroduodenal flux regulation simulation, antacid activity duration was rapid and included between 85 and 118 min in NS situation (50 to 56 mmol H+ consumed) and between 75 and 93 min in DU situation (43 to 47 mmol H+ consumed). The reduction of acid load penetrating into the duodenum was contained between 36 and 50 per cent. Effervescent compounds exerted a neutralising activity and a buffering capacity close to pH 6.0 (5 per cent of total antacid capacity), related to antacid potency.

Antacids↗

[A clinical trial on the effect of aluminum containing antacids on the course of duodenal ulcer healing and morphology of the gastric mucosa].

We carried out the controlled, double-blind clinical study on the effect of antacids containing aluminium on the healing of duodenal ulcer (DU) and the morphology of gastric mucosa in 153 patients with duodenal ulcer disease. The patients were treated for 4 weeks with either dihydroxyaluminium-sodium carbonate (Alugastrin) or aluminium and magnesium hydroxides (Alumag) and for comparison with ranitidine or placebo. The clinical usefulness of antacids were assessed according to the following criteria: ulcer healing ratio, disappearance of ulcer pain, drug tolerance both subjective and objective (biochemical analyses) and drug effect on the gastric mucosa (endoscopy, histology and morphometry). The results were compared with results obtained from ranitidine treated patients. We have shown that both antacids speed up the DU healing similarly to ranitidine (71%, 75% and 79% respectively) and significantly better than placebo (47% of cases). All administered drugs diminished subjective symptoms of patients and were well tolerated. Dihydroxyaluminium-sodium carbonate and aluminium and magnesium hydroxides as well as ranitidine were without any trophic effects on the gastric mucosa. Thus, despite differences in the pharmacological action (antacids are gastroprotective drugs, ranitidine inhibits HCl secretion), antacids are similarly effective to ranitidine in the treatment of DU patients. However, ranitidine is more comfortable for the patients and better accepted in the long-term treatment.

Adult↗

[Gastroprotective effect of an antacid coating agent in rats. Role of endogenous prostaglandins, capsaicin-sensitive afferents neurons and nitric oxide].

UNLABELLED: The aims of this study were: a) to demonstrate the gastroprotective effect of the antacid and mucosal coating agent Gastralgine (aluminium hydroxide and glycinate, magnesium trisilicate and simeticone) against ethanol- and indomethacin-induced gastric injury in the rat; b) to investigate whether gastroprotection elicited by this agent involves stimulation of capsaicin sensitive afferent neurons and activation of the nitric oxide system. METHODS: Rats received intragastrically 2 mL of the antacid or distilled water followed 1 hr later by 2 mL of 100% ethanol ig or 30 mg of indomethacin sc. The surface of ethanol-induced lesions and the length of indomethacin-induced lesions were measured. The role of afferent neurons and endogenous nitric oxide in the prevention of ethanol-induced gastric damage was determined using respectively capsaicin and the inhibitor of nitric oxide biosynthesis, NG-nitro-L-arginine. RESULTS: The antacid and mucosal coating agent significantly reduced the area of macroscopic lesions induced by ethanol and the length of lesions induced by indomethacin. Both functional ablation of afferent nerves and inhibition of nitric oxide synthesis significantly increased ethanol-induced gastric injury but failed to reverse the gastroprotective effect of the antacid against 100% ethanol. CONCLUSIONS: The antacid and mucosal coating agent Gastralgine has a gastroprotective effect against ethanol- and indomethacin-induced injury in the rat. This property does not involve stimulation of capsaicin sensitive afferent neurons or synthesis of endogenous nitric oxide.

Animals↗

The hypocholesterolemic effect of an antacid containing aluminum hydroxide.

STUDY OBJECTIVE: To evaluate the efficacy, safety, and hypocholesterolemic effect of an aluminum hydroxide-containing antacid in hypercholesterolemic individuals. DESIGN: A prospective, randomized, double-masked, placebo-controlled phase of 2 months' duration, followed by an open-design treatment phase of 2 months' duration and a washout phase of 2 months' duration. SETTING: Family practice clinics of two rural communities (kibbutzim) in Israel. PATIENTS: Fifty-six men and women with hypercholesterolemia (type IIa or IIb). Fifty individuals completed the study. INTERVENTION: After 2 months of dietary modification (low-fat, low-cholesterol diet), the participants were randomized into two matched groups. Group 1 (28 participants) was treated for 2 months with a chewable antacid tablet containing simethicone, magnesium hydroxide, and 113 mg of aluminum hydroxide per tablet, at a dose of two tablets four times daily. Group 2 (22 participants) was given a similar number of placebo tablets for 2 months. During the following 2 months, both groups received the antacid at the above dose. MEASUREMENTS AND MAIN RESULTS: Lipoprotein levels were evaluated at baseline and every 2 months thereafter for 6 months. Compared with pretreatment levels, Group 1 experienced a decrease in low-density lipoprotein cholesterol (LDL-C) of 9.8% after 2 months (p less than 0.001) and 18.5% after 4 months (p less than 0.001). Compared with Group 2, the decrease in LDL-C in Group 1 was 6.2% at the end of the 2-month double-masked, placebo phase. Although the high-density lipoprotein cholesterol (HDL-C) was also reduced in Group 1 at the end of 4 months of therapy (10.2%), the HDL-C/LDL-C ratio increased by 13% during the same interval (p less than 0.05). The treatment was well tolerated, with minimal side effects. CONCLUSIONS: An aluminum hydroxide-containing antacid reduces LDL-C in hypercholesterolemic individuals. Although HDL-C was also reduced to a lesser extent, the overall atherogenic index was improved. Further studies should be conducted to evaluate the long-term safety and efficacy of antacids containing aluminum hydroxide in hypercholesterolemic patients.

Adult↗

The effect of antacid on aspirin pharmacokinetics in healthy Thai volunteers.

The effect of antacid on aspirin pharmacokinetics and bioavailability was determined in 10 healthy adult male and female volunteers, aged 20-45 years old. Each subject received 650 mg of aspirin orally after an overnight fast. The wash out period was 14 days and then all subjects were given 650 mg of aspirin 10 minutes after antacid (aluminium hydroxide and magnesium hydroxide). Plasma aspirin, salicylate and salicyluric acid levels were determined by a specific high performance liquid chromatographic analysis. Individual plasma profiles were analysed using compartmental and non-compartmental methods. The results show that antacid affected the relative bioavailability of aspirin since the mean peak concentration (Cmax) of aspirin was significantly higher when antacid was given. However, the time to reach peak concentration (Tmax) and the area under the plasma concentration-time curve (AUC) showed no significant difference between the two treatments. It was, therefore, not possible to conclude that the non-bioequivalence was caused by a difference in rate or amount of aspirin absorption, or both. No significant difference was observed in Cmax, Tmax, AUC, t1/2, Ka, Kel of salicylate and salicyluric acid. However, the rate of total salicylate absorption was increased since the absorption rate constant (Ka) was higher when antacid was given. This may provide a more rapid effect of the drug.

Adult↗

Mineral-metabolic side effects of low-dose antacids.

Mineral-metabolic side effects of a low dose of a conventional Al-Mg antacid were examined in 10 healthy volunteers, who were given one antacid tablet after the 3 main meals and at bedtime (buffering capacity, 120 mmol/day) for 4 weeks. Compared with the pre-medication state, the following changes of statistical significance occurred during antacid ingestion: increase in urinary excretion of magnesium, calcium, and aluminum; decrease in urinary excretion of phosphate; increase in maximal renal phosphate reabsorption (Tm PO4/GFR); and increase in serum concentration of aluminum. Most of the changes were normalized 3-4 days after cessation of antacid medication. There was no change in intestinal absorption of calcium. The fact that even this low dose of antacids can provoke measurable changes in mineral metabolism, including aluminum absorption, is noteworthy, although we did not see any clinical symptoms from the biochemical changes.

Adult↗

CONSTANT INTRAESOPHAGEAL ANTACID DRIP AS A METHOD OF TREATMENT OF REFLUX ESOPHAGITIS.

Fifteen cases of intractable chronic esophagitis due to gastroesophageal reflux were treated with a continuous intraesophageal antacid drip. A proprietary antacid preparation, Gelusil or monalium hydrate (Riopan), in a concentration of one part of antacid to nine parts of water, was infused into the mid-esophagus through a polyethylene tube with an internal diameter which admits a No. 18 blunted needle. Patients are not confined to bed while the drip is in progress. If the flow is constant and the end of the tube is below the cricopharyngeal sphincter, patients do not experience discomfort even if the drip is administered continuously for several days.Results indicate that remission of symptoms can be achieved in almost every patient, even those who have previously failed to respond to oral antacid therapy.

Aluminum Hydroxide↗

Effects of sucralfate vs antacids on gastric pathogens: results of a double-blind clinical trial.

BACKGROUND: Unblinded studies suggested that sucralfate prophylaxis for stress ulcers is associated with a lower rate of nosocomial pneumonia than acid-reducing approaches. We performed a randomized, double-blind, double-sham clinical trial comparing the exact microbial effects of each treatment. METHODS: One hundred forty patients entered this study before major elective surgery, allowing baseline cultures of gastric and pulmonary secretions to be obtained intraoperatively. Postoperatively, the patients were treated with standard doses of either sucralfate or antacids, plus a sham of the other drug. Cultures were repeated twice daily for 3 days. Molecular epidemiological typing was used to track the appearance of specific microbes and their transmission from site to site, and clinical end points were compared. The number of patients chosen was for sufficient statistical power to detect differences in the microbial measures, as detecting differences in clinical measures would have required increasing the sample size by an order of magnitude. RESULTS: Gastric pH was affected by the form of stress ulcer prophylaxis throughout the study, and this pH effect affected the number of new gastric organisms appearing in the 2 different groups. Colonization of the airway with new gastric organisms occurred more frequently in the antacid than in the sucralfate group, and colonization of the airway with organisms of gastric origin was associated with occurrence of postoperative pneumonia. CONCLUSIONS: Both sucralfate and antacids offered safe and effective stress ulcer prophylaxis in this double-blind clinical trial of postoperative patients in an intensive care unit. In association with the drug's effects on gastric pH, more new pathogens appeared in the gastric contents of antacid-treated than sucralfate-treated patients.

Antacids↗

Cimetidine vs antacid in prophylaxis for stress ulceration.

Seven-seven critically ill patients were prospectively randomized into four groups to compare antacids and various doses of cimetidine in the neutralization of gastric acid for preventing complications of stress ulcers. Gastric pH was monitored hourly, basing the efficacy of neutralization on preselected pH values for each study group. Cimetidine provided adequate neutralization in 14 (23%) of 61 patients. Gastric acid in all 16 patients treated with antacids was adequately neutralized. Stress bleeding occurred in three (5%) patients treated with cimetidine and in no patient treated with antacids. Reversible thrombocytopenia developed in six (26%) of 23 patients treated with 2,400 mg/day of cimetidine. Hourly monitoring of gastric pH is a mandatory component in the prevention of stress bleeding. Antacid is the preferred agent for gastric acid neutralization because it is more effective, safer, and less expensive.

Adolescent↗

Comparison of antacids on the binding of bile salts.

Following a gastric operation (and occasionally in other patients), biliary reflux may damage the stomach mucosa. If severe damage occurs, a diverting Roux-en-Y procedure may be required. In most cases, nonoperative treatment is successful. Since bile salts have been implicated as a cause of mucosal injury, we evaluated the efficacy of antacids in binding these salts. Several bile salts were mixed with certain antacids and with cholestyramine resin, and the adsorption was determined. Cholestyramine resin absorbed 90% to 97% of the bile salts. At a pH of 7, magaldrate (Riopan) absorbed the dihydroxy-bile salts as well as cholestyramine resin, but the other antacids we tested showed poor adsorption. The ability of antacids to bind bile salts must be considered when treating bile salt-induced injury with these substances.

Adsorption↗

Antacid vs sucralfate in preventing acute gastrointestinal tract bleeding in abdominal aortic surgery. A randomized trial in 50 patients.

We carried out a randomized, controlled trial of sucralfate vs antacid as prophylaxis against upper gastrointestinal tract bleeding in 50 patients who had undergone abdominal aortic surgery. The groups were similar in age, sex, duration of prophylaxis, and number of risk factors per patient. No patient in the antacid group had upper gastrointestinal tract bleeding. One patient in the sucralfate group had frank bleeding from the nasogastric tube; however, she also had a coagulopathy and thrombocytopenia. The bleeding stopped when these conditions were corrected. No complications occurred in the sucralfate group; five patients in the antacid group had minor complications. Sucralfate was as effective as antacid in this trial, and it resulted in a considerable saving in nursing time.

Aged↗

Effect of antacids on absorption of clorazepate.

The effect of a magnesia and alumina antacid suspension on the absorption of clorazepate dipotassium was studied in 15 normal healthy adult subjects who ingested a 15-mg dose of clorazepate alone or with single or multiple doses of antacid. The results of this three-period randomized complete crossover study showed a trend of initially slower absorption and lower peak nordiazepam plasma levels when administered with the antacid suspension. However, there were no significant differences among treatments in the extent of absorption as measured by the area under the plasma level-time curves. Clorazepate plasma levels were of relatively short duration and similar for all treatments. The urinary excretion pattern was likewise comparable with conjugated oxazepam, the major species measured. Plasma elimination half-lives of nordiazepam and clorazepate were not affected by the antacid treatments.

Adult↗

Interactions of cimetidine and ranitidine with aluminum-containing antacids and a clay-containing gastric-protective drug in an "artificial stomach-duodenum" model.

Interactions of cimetidine and ranitidine with aluminum-containing antacids and clay-containing gastric-protective drugs were analyzed in vitro by using an artificial stomach-duodenum model. The model reproduced near-physiologic conditions, taking into account gastric and duodenal flux variations and interactions between gastric mucosa and drugs added to the gastric content. Clay bound cimetidine in acid medium, but the drug was released when the pH increased, resulting in cimetidine amounts in the duodenal site close to those in controls. In contrast, clay bound ranitidine in acid medium and did not release it in the duodenal site. Aluminum-containing antacids did not significantly modify the amount of cimetidine or ranitidine available for absorption. Several factors play a role in the interactions of cimetidine and ranitidine with aluminum-containing antacids and clay-containing gastric-protective drugs: the structure of the antisecretory drugs, gastroduodenal pH, interactions of the antacid and clay with the gastric mucosa, and release of aluminum that could adsorb the drugs or prevent their adsorption by the mucosa. These phenomena are intricate and difficult to analyze without using a physicochemical approach.

Aluminum↗

pH-control via secretin or antacid: prophylaxia of stress ulcers in high-risk surgical patients.

The efficacy of an antacid or synthetic secretin in elevating the intragastric pH above 4 was tested in a controlled, prospective study. Twenty-one high-risk surgical patients received an antacid and 17 secretin. Antacid prophylaxis resulted in a significantly higher intragastric pH than with secretin. This was especially true in patients with several risk factors. The percent of secretin patients with a pH below 4 was higher. An increase in dosage was necessary in 4 of the 17 patients receiving secretin and in none of those receiving antacids. One stress ulcer hemorrhage occurred during secretin prophylaxis.

Aged↗

Effect of two antacids on the bioavailability of paracetamol.

The effect of two antacids on the bioavailability of paracetamol has been investigated in 12 young healthy volunteers. Following a random cross over design, each subject swallowed, on three separate occasions, one weak apart, 500 mg paracetamol alone, or together with two different aluminium hydroxide, magnesium hydroxide preparations (Dimalan and Maalox). Plasma paracetamol levels were measured by HPLC. The bioavailability of paracetamol was not altered by either antacid, but they both delayed the time to peak plasma concentration (0.85 h; 1.43 h; 1.25 h, without antacid, with Dimalan and with Maalox respectively). The peak plasma concentration was not affected by concurrent antacid administration.

Acetaminophen↗

Antacid vs placebo in hospitalized gastric ulcer patients: a controlled therapeutic study.

Antacids are widely accepted as agents that promote healing and relieve pain of gastric ulcer. Well-controlled studies designed to test this belief are few. 28 patients with endoscopically proven gastric ulcer were treated for 3 weeks in hospital, 13 receiving a liquid placebo and 15 an antacid. All were followed by endoscopy to complete healing or until surgery was performed. 10 patients healed satisfactorily in the placebo group and 11 in the antacid group. All patients were free of pain during their hospitalization. From this study it is concluded that in gastric ulcer patients hospitalized for 3 weeks, the rate of healing of the ulcer and the relief of pain is not influenced by treatment with a standard antacid preparation.

Alcohol Drinking↗