Antacids

Comparative studies

Effervescent ranitidine 150 mg bd has been compared with as-needed calcium carbonate antacids 750 mg in a randomized study in 115 subjects who frequently self-treated heartburn [ ]. Effervescent ranitidine was significantly more effective than antacids in reducing heartburn, healing erosive esophagitis, alleviating pain, and improving quality of life. The overall incidences of adverse events were not significantly different in the two groups; 12% in the antacid group and 3% in the ranitidine group had adverse events related to the gastrointestinal system: nausea, vomiting, diarrhea, constipation, gas, fecal incontinence; and 1% in the antacid group and 4% in the ranitidine group had adverse events related to the central nervous system: headache, dizziness, insomnia, malaise, fatigue, weakness, nervousness.

Hydrotalcite and famotidine have been compared in an open, randomized, parallel-group study in 53 patients with endoscopically proven gastroesophageal reflux disease, of whom 26 received a single dose of hydrotalcite 1 g and 27 a single dose of famotidine 10 mg for episodes of symptomatic reflux [ ]. Hydrotalcite was significantly superior to famotidine in increasing the proportion of responders within the first 45 minutes, starting 10 minutes after drug administration. At 60–120 minutes both compounds were equally efficacious. There were no adverse events in either group.

Sodium alginate and anhydrous magaldrate were compared in an open, randomized, parallel trial of 191 patients aged 18 and over with symptoms of gastroesophageal reflux [ ]. Sodium alginate had a statistically significant faster onset of action and was more efficacious. Diarrhea and nausea were noted in five of 93 patients who took alginate, and seven of 98 who took magaldrate [ ]. There were no drug-related serious adverse events. Sodium alginate, omeprazole, ranitidine, and placebo have been compared in a single-center, open, crossover study in 19 adults aged 18–70 with gastroesophageal reflux. Nausea attributed to ranitidine was the only adverse effect. No serious adverse events were reported.

Placebo-controlled studies

In a randomized, placebo-controlled, four-way, crossover study of the effects of low-dose ranitidine and an antacid on meal-induced heartburn and acidity in 26 subjects, ranitidine 75 mg significantly reduced gastric but not esophageal acidity, calcium carbonate 420 mg significantly reduced esophageal but not gastric acidity, and ranitidine plus calcium carbonate reduced both esophageal and gastric acidity [ ]. Both drugs given alone reduced heartburn severity compared with placebo.

General adverse effects and adverse reactions

When they are given in conventional doses for symptomatic relief, antacids are safe, and adverse effects seldom limit the choice of formulation, except when troublesome diarrhea occurs [ ]. Change of bowel habit, usually in the form of mild diarrhea, is common, especially with magnesium salts. Other adverse effects usually occur as a direct consequence of ion absorption. They include alkalosis (particularly with large doses of soluble antacids), milk alkali syndrome when calcium is included, and the consequences of absorbing individual ions, particularly sodium but also bismuth and aluminium. Heart failure can be precipitated in susceptible patients by antacids with a high sodium content (see the Cardiovascular section). Antacids can interfere with the absorption of other drugs to a clinically important extent. Allergic reactions and tumor-inducing effects have not been described.