Changes in potential difference across the human buccal mucosa with buffered or unbuffered aspirin and salicylate.

The potential difference (PD) across the gastric mucosa is an index of mucosal integrity, and is lowered by topical application of irritants such as aspirin. There are basic similarities in the PD across the buccal and gastric mucosae, and we have therefore investigated the actions of various salicylates in buffered or un-buffered solution on buccal PD in human subjects. Aspirin (at pH 2) and soluble aspirin (pH 4.4) applied topically reduced buccal PD, but this fall was abolished by buffering to pH 7. Sodium salicylate likewise reduced buccal PD at pH 4 and pH 6, but not when buffered to pH 7. Two other soluble aspirin mixtures also reduced buccal PD, indicating insufficient buffering capacity to prevent topical irritancy. Ingestion of aspirin (600 mg), avoiding topical contact with the buccal mucosa, did not alter buccal PD. Paracetamol applied topically likewise failed to reduce buccal PD. Measurement of buccal PD may be useful in the preliminary assessment of the gastrointestinal irritation provoked by anti-inflammatory and other compounds.