Evaluation of an enteric coated aspirin preparation.

The bioavailability and gastrointestinal site of release of enteric coated aspirin tablets ("Rhusal", G.P. Laboratories) were investigated following dosage with single tablets. A delay of one to more than eight hours was observed between dosage and the appearance of salicylate in plasma or saliva. This delay was decreased by pretreatment with metoclopramide. No aspirin or salicylate was detected in gastric aspirates. The mean urinary recovery of salicylate was equivalent to 92% of the administered dose. All these tests were consistent with the designed function of the enteric coating. The time course of concentrations of salicylate in saliva rather than in plasma was confirmed as a useful technique for the evaluation of different formulations of aspirin. The acceleration of gastric emptying by metoclopramide is a useful technique for the evaluation of enteric coated tablets.