Digestive D&eases and Sciences, Vol. 30, No. 12 (December 1985), pp. 1127-1133 Liberation of Hydrogen from Gastric Acid Following Administration of Oral Magnesium DAVID A. SACK, MD, and CHARLES BOLT STEPHENSEN, PhD We are in the process of developing a noninvasive test for gastric acid secretion based on the reaction of orally administered magnesium metal with gastric acid: Mg + 2HC1 --~ MgCl2 + H2. We hypothesized that the hydrogen gas thus evolved could be detected in exhaled air and belches and that the amount of hydrogen released could be related to the amount of acid in the stomach. To validate this hypothesis, we gave magnesium to two groups of young adult volunteers following either betazole stimulation or cimetidine inhibition of acid secretion. In group I we gave subcutaneous betazole and gave magnesium in doses from 10 to 200 mg. In group II we gave oral betazole and used a constant dose of 150 mg of magnesium. In both groups we consistently detected significant increases in breath and belch hydrogen following magnesium in the betazoIe- stimulated volunteers. This response was blocked by cimetidine. The magnitude of the response was related to the magnesium dose, with 150 mg appearing to induce a maximum response. Administration of oral magnesium up to 200 mg was not associated with any untoward effects. We conclude that magnesium led to the release of hydrogen gas in vivo and that the quantity of hydrogen gas recovered was related to the amount of gastric acid. With further development, this principle might be used to develop a simple noninvasive test for gastric acid secretion. Gastric acid secretion is important in several dis- ease conditions. Elevated levels are seen with Zol- linger-Ellison syndrome and decreased levels are seen in pernicious anemia and in some patients with gastric carcinoma (1, 2). Hypochlorhydria predis- poses to infectious diarrheas, especially those due to Vibrio cholerae and Escherichia coli (3-9). Al- though drugs are commonly used in peptic ulcer Manuscript received May 3, 1984; revised manuscript received November 28, 1984; accepted March 25, 1985. From the Division of Geographic Medicine, The Johns Hop- kins University School of Medicine, and Francis Scott Key Medical Center, 4940 Eastern Avenue, Baltimore, Maryland 21224. This work was supported by a grant from the Nestle Coordi- nation Center for Nutrition, Inc. Address for reprint requests: Dr. David A. Sack, Francis Scott Key Medical Center, 4940 Eastern Avenue, Baltimore, Mary- land 21224. disease to block or neutralize gastric acidity (10, 11), they are used without documenting their phys- iological effectiveness in decreasing acidity in the individual patient. Gastric acid secretion is generally measured by aspirating stomach contents via a nasogastric tube after parenteral administration of a gastric stimulant such as betazole or pentagastrin (12). The volumes of these specimens are measured, and samples are titrated to neutrality with sodium hydroxide to determine their acid content. A major disadvantage of this method is that the discomfort associated with nasogastric intubation makes the test unacceptable to many patients. We are hoping to develop a noninvasive, tubeless method to measure gastric acid secretion which would be useful in a clinic or even field setting. The Digestive Diseases and Sciences, VoL 30, No. 12 (December 1985) 0163-2116/85/1200-1127504.50/0 9 1985 Plenum PublishingCorporation 1127