Influence of food on aspirin absorption from tablets and buffered solutions

After a standard meal, 12 normal volunteers received three aspirin dosage forms in a single-dose, complete crossover study. The three dosage forms were an unbuffered tablet, an effervescent solution with 16 meq of buffer, and an effervescent solution with 34 meq of buffer. Plasma and urine aspirin, salicylic acid, and salicyluric acid were measured for 10 hr. Significant differences in the absorption kinetics of aspirin were observed, with aspirin from the two solutions being absorbed faster than from the tablet. Urine pH and renal clearance for all three acid compounds were influenced by the buffer during the first 2 hr only. Area under the curve (AUC) and urine accumulation comparisons suggest that 15-20% more aspirin reaches the general circulation after the tablet, but that the total salicylate absorbed is not different. Comparison with an earlier study indicates the solution with 34 meq of buffer is virtually unaffected by the presence of the meal while the solution with 16 meq buffer and the tablet are more slowly absorbed in the nonfasted state.