Nizatidine is a selective histamine H₂-receptor antagonist that inhibits histamine-mediated gastric acid secretion. Dosages of 150 mg and 300 mg administered twice a day or at bedtime are approved for the treatment of active duodenal and gastric ulcers, and erosive esophagitis. A lower-dose, over-the-counter formulation is now available for the prevention of postprandial heartburn. Spiegel and associates compared the effectiveness of three different dosages of nizatidine (225 mg, 75 mg and 25 mg) in preventing postprandial heartburn.

A total of 413 subjects were randomized to receive one of the three dosages or placebo. They were given the drug 30 minutes before a meal of chili, cheese-flavored nacho chips and cola. Only 2.9 percent of the subjects receiving placebo had complete prevention of heartburn. In the nizatidine groups, 14.4 percent of the subjects receiving the 225-mg dose and 14.9 percent of those receiving the 75-mg dose had complete prevention of heartburn. The results in the treatment group that received 25 mg of nizatidine were not distinguishable from those in the placebo group.

The longest duration of complete heartburn relief following the meal was significantly greater for all nizatidine treatment groups, compared with the placebo group. All three dosages of nizatidine significantly reduced the average severity of heartburn, compared with placebo. In those subjects whose heartburn was not completely prevented, all dosages of nizatidine were equally superior to placebo in reducing the average severity and peak severity of heartburn. All dosages of nizatidine were well tolerated.

The authors conclude that 75-mg and 225-mg dosages of nizatidine administered 30 minutes before eating a meal that provokes heartburn are effective in providing complete heartburn relief. These two dosages were significantly better than placebo and the 25-mg dosage in preventing postprandial heartburn. The authors conclude that the 75-mg and 225-mg dosages of nizatidine are effective in preventing postprandial heartburn, despite the fact that these dosages are lower than that available in the prescription formulation.