Effect of several drugs on gastric potential difference in man.

Measurement of gastric mucosal potential difference was used to study the effect on the gastric mucosal barrier in six volunteer subjects of several drugs known to provoke ulcers. Potential differences were also recorded in nine patients with rheumatoid arthritis being treated with long-term aspirin and five patients on long-term prednisone. Unbuffered aspirin and ethanol "broke" the barrier as shown by a rapid fall in potential difference. The effects of aspirin were dose related, with 600 mg causing a greater reduction than 300 mg. The effects of aspirin and ethanol given together were additive and caused the greatest fall in potential difference. Sodium acetylsalicylate did not alter the normal potential difference. Indomethacin, phenylbutazone, and prednisone all failed to cause any change in potential difference. The patients on long-term aspirin and prednisone had readings within the normal range and responded the same as normal subjects to an acute challenge. These studies show that aspirin and ethanol will damage the gastric mucosal barrier but that indomethacin, phenylbutazone, and prednisone do not.