Effects of low doses of erythromycin on the ¹³C Spirulina platensis gastric emptying breath test and electrogastrogram: A controlled study in healthy volunteers

OBJECTIVE: Electrogastrography and stable isotope gastric emptying breath tests (GEBTs) are relatively simple, non-invasive tests of gastric motor function that may be useful in monitoring the effects of therapeutic interventions. It was our primary objective to examine the effects of low dose i.v. erythromycin on the results of the ¹³C Spirulina platensis GEBT and electrogastrography. We were also interested in evaluating the reproducibility of these tests. METHODS: In 10 healthy subjects (five female, ages 23-37 yr), we simultaneously performed the GEBT, using a pre-packaged meal (340 kcal), and electrogastrography on each of four different occasions separated by at least 1 wk. After performance of baseline studies, they were repeated in random order after the infusion of 50 mg of erythromycin (Er50), 100 mg erythromycin (Er100), and a placebo (saline). Breath samples were obtained at baseline and at 75, 90, and 180 min after the meal and T_1/2 and T_lag calculated. Electrogastrography recordings began 30 min before the test meal and continued for 2 h after the meal. RESULTS: Baseline and placebo T_1/2 and T_lag were similar. Er50 resulted in a modest acceleration of gastric emptying (T_1/2 Er50 vs baseline vs placebo = 104.0 vs 132.7 vs 125.5 min) and reduction in lag time (T_lag Er50 vs baseline vs placebo = 47.2 vs 61.5 vs 56.2 min). A similar decrease was seen in response to Er100. The baseline and placebo fasting and fed electrogastrography parameters were similar. After infusion of Er100, the percentage of normal slow waves in the first postprandial hour decreased relative to baseline and placebo (percent normogastria Er100 vs baseline vs placebo = 64.1 ± 7.5 vs 82.4 ± 6.4 vs 79.7 ± 5.5). This corresponded with an increase in percent tachygastria during the same period and an overall decrease in the mean dominant frequency. Similar but less striking changes were seen after administration of Er50. Replicate GEBTs showed a high degree of reproducibility both within and between individuals for T_1/2 and T_lag. In contrast, replicate electrogastrograms revealed moderate to high variability for all parameters except the dominant frequency. CONCLUSION: The stable isotope GEBT utilizing ¹³C S. platensis demonstrates responsiveness to the prokinetic effects of low dose i.v. erythromycin and good reproducibility.