The influence of codeine, propantheline and metoclopramide on small bowel transit and theophylline absorption from a sustained-release formulation

Effect of food on gastrointestinal transit of liquids in cynomolgus monkeys

We investigated the gastrointestinal transit of liquids, as well as various gastric pH profiles, in fed cynomolgus monkeys. Twelve grams of a biscuit-type solid food were provided 1 h before the test. The acetaminophen method was used to determine the gastric half-emptying time (t(50%)), which provided an estimate of the gastric emptying rate. The gastric emptying rate of liquids was significantly reduced after food intake in monkeys. The mean t(50%) value was 143.5 min and comparable to that of humans after eating. However, there was a large variability in the t(50%) between individual animals as shown by the coefficient of variance of approximately 80%. Next, the median oro-caecal transit time in fed monkeys was determined to be 1.8 h, using the sulfasalazine-sulfapyridine method. There was no significant difference in oro-caecal transit time between unfed and fed monkeys; thus, food intake has no significant effect on the oro-caecal transit time of liquids in either monkeys or humans. However, the oro-caecal transit time in humans is about 2 h longer than that in monkeys. Our experiments using several different foods suggested that the typical human gastric pH profile could not be simulated in fed monkeys.

Gastrointestinal transit of liquids in unfed cynomolgus monkeys

In this study, the gastric emptying rate and oro-caecal transit time of two liquid volumes (20 and 60 ml) were compared in unfed cynomolgus monkeys. First, the acetaminophen method was used to determine the gastric half-emptying time (t(50%)). The mean t(50%) from seven monkeys was 21.2 min for the 20-ml volume and 27.8 min for the 60-ml volume. This mean t(50%) in monkeys is similar to that reported previously in fasting humans. Next, the sulfasalazine-sulfapyridine method was used to determine median oro-caecal transit times for the 2 liquid volumes; these times were 2.5 h for the 20-ml volume and 2.3 h for the 60-ml volume, which are about 1.5 h shorter than previously reported transit times in humans. An increase in volume administered did not significantly change either the t(50%) or oro-caecal transit time. The data also show that variability in both t(50%) and oro-caecal transit time within each monkey is not as great as the large variability between monkeys. Consequently, cynomolgus monkeys are good model animals to use for studies on the gastric emptying of drug-containing liquids after fasting; however, analysis of results from bioavailability studies must compensate for differences in the oro-caecal transit time between monkeys and humans.

Orocecal transit time in humans assessed by sulfapyridine appearance in saliva after sulfasalazine intake

PURPOSE

We propose a noninvasive method for the measurement of orocecal transit time assessed by the sulfapyridine appearance time in saliva after ingestion of sulfasalazine.

METHOD

In 12 healthy volunteers, we studied the correlation between plasma and saliva sulfapyridine appearance times and then the sulfapyridine appearance times in saliva under various experimental conditions to assess the reproducibility, the effects of meals, and the role of the formulation, and the effects of gastrointestinal kinetic drugs.

RESULTS

The correlation between saliva and plasma sulfapyridine appearance times was strong (r = 0.84; p = 0.0004). The sulfapyridine saliva appearance time was significantly delayed by the meal. Compared with placebo, the saliva sulfapyridine appearance time was reduced by cisapride (312 +/- 128 versus 551 +/- 97 minutes; p = 0.0001) and increased by loperamide (674 +/- 267 versus 501 +/- 131 minutes; p = 0.044).

CONCLUSION

We propose the salivary sample method as a validated simplification of the plasma sulfasalazine-sulfapyridine test for the measurement of orocecal transit time.