AIM: To determine the effect of oral erythromycin on gastric and small bowel transit time of capsule endoscopy.

METHODS: Consecutive patients who underwent capsule endoscopy during the 16-mo study period were either given 250 mg oral erythromycin, 1 h prior to swallowing the capsule endoscope or nothing. The gastric and small bowel transit time, and the small bowel image quality were compared.

RESULTS: Twenty-four patients received oral erythromycin whereas 14 patients were not given any prokinetic agent. Patients who received erythromycin had a significantly lower gastric transit time than control (16 min vs 70 min, P = 0.005), whereas the small bowel transit time was comparable between the two groups (227 min vs 183 min, P = 0.18). Incomplete small bowel examination was found in three patients of the control group and in one patient of the erythromycin group. There was no significant difference in the overall quality of small bowel images between the two groups. A marked reduction in gastric transit time was noted in two patients who had repeat capsule endoscopy after oral erythromycin.

CONCLUSION: Use of oral erythromycin significantly reduces the gastric transit time of capsule endoscopy.

The introduction of wireless capsule endoscopy, which has made direct visualization of the small bowel possible, has opened up a new chapter on small bowel imaging. Initial comparative studies showed that wireless capsule endoscopy is superior to push enteroscopy[1-4] or conventional radiological imaging[5]. The wireless capsule endoscopy is approved by the Food and Drug Administration of USA and is particularly useful for the diagnosis of obscure gastrointestinal bleeding.

With the limited battery life, the current capsule endoscope could take images for up to 8 h. Any delay in gastric transit may inadvertently result in incomplete small bowel examination. Whilst the capsule endoscope is passively propelled by peristalsis down the intestinal lumen, it is impossible to predict the time required for the capsule endoscope to navigate through the stomach. Although the use of prokinetic agents may potentially speed up the gastric emptying time, the effect of prokinetic agents on the outcome of wireless capsule endoscopy remains undetermined. Among various prokinetic agents, erythromycin, a motilin agonist, has been used to speed up gastric emptying in patients with gastroparesis[6-8]. Moreover, the use of intravenous erythromycin has been shown to improve the quality of upper gastro-intestinal endoscopy in patients with upper gastro-intestinal bleeding, possibly via emptying of the blood contents within the stomach[9]. Here, we determined the effects of oral erythromycin on the gastric and small bowel transit time of the capsule endoscope as well as the quality of small bowel images in patients undergoing capsule endoscopy.

As gastric and small bowel transit time shows considerable inter-individual variations and the prime interest of the capsule endoscopy is to examine the small bowel only, ways to enhance gastric transit time without compromising small bowel examination would potentially improve the outcome of this investigation. However, the effect of prokinetic agent on this relatively new examination remains elusive. In this study, we specifically addressed the effect of oral erythromycin on gastric and small bowel transit time in patients undergoing capsule endoscopy.

Erythromycin promotes gastric emptying by binding to motilin receptors and acts as a motilin agonist. The use of low dose intravenous erythromycin has been shown to improve gastric emptying in patients with diabetic gastroparesis[7]. Moreover, erythromycin infusion prior to endoscopy in patients with recent hematemesis has been shown to make endoscopy easier, and reduces the need for a repeat procedure by enhancing the emptying of blood within the stomach[9]. Results from this study showed that the use of low dose oral erythromycin could enhance gastric transit time of the wireless capsule endoscopy. The gastric transit time in the 24 patients who received erythromycin was all within 60 min. In contrast, 5 (36%) patients in the control group had gastric transit time of more than 1 h. In a previous volunteer study, it was noted that the mean gastric transit time of capsule endoscopy is 63 min (range 10-319 min)[10]. This result is comparable to the findings in our control group. To further support our findings, there was a marked reduction in gastric transit time in the two patients who used oral erythromycin on the second examination only.

Other than speeding up the gastric transit time, the use of erythromycin was not associated with any significant changes in small bowel transit time. On the other hand, patients receiving erythromycin tended to have a higher rate of complete small bowel examination. This is probably due to the shortened gastric transit time instead of alterations in small bowel passage by the use of erythromycin. More importantly, the use of erythromycin did not appear to alter the overall quality of small bowel images. The percentage of “unsatisfactory” small bowel images reported in this study was relatively high, which may be related to the use of very stringent criteria for satisfactory images, i.e., >90% clear and optimal images. Moreover, we did not use any bowel cleansing agent in this study, which may further improve the quality of small bowel images[11]. It was shown in a small uncontrolled study that the use of polyethylene glycol may also shorten the transit time of the capsule endoscopy through the stomach and small bowel[12]. It remains to be determined whether the combined use of prokinetic agents and bowel cleansing agent has synergistic effect on small bowel transit time.

Erythromycin is a safe and cheap antibiotic, which can be conveniently given via oral route. It is also relatively free of adverse reactions including drug sensitivity. Although most published data used an intravenous preparation of erythromycin, we found that the use of oral dosage was also effective for this purpose. Apart from erythromycin, there are several other prokinetic agents that may be used in reducing gastric transit time during capsule endoscopy. Cisapride, which was previously used as a gastric prokinetic agent, is associated with fatal arrhythmia in susceptible individuals[13,14] and has been withdrawn by the Food and Drug Administration in 1999[15]. Domperidone and metoclopramide are also used in treating symptomatic patients with gastroparesis. However, the latter is not infrequently associated with extra-pyramidal side effects. Recently, the 5-HT4 receptor partial agonist, tegaserod, is found to accelerate gastric emptying and gastro-intestinal transit time in healthy male subjects[16]. Whether these drugs can also be used as prokinetic agents for capsule endoscopy remains to be determined and it is interesting to compare the effects of different prokinetic agents in future studies.

Although this was a non-randomized study, most of the potential confounding factors were comparable in the two groups. All demographic and clinical details of the two groups were matched. Moreover, all viewers were blinded to the clinical information of the patients. With the shortened gastric transit time, it is not difficult to anticipate that the time spent by the examiners on reviewing the images would be reduced accordingly. This may be another advantage of using prokinetic agents in this rather time-consuming examination.

In summary, erythromycin given orally prior to swallowing capsule endoscope significantly reduces the gastric emptying time without compromising small bowel transit time and image quality. Further randomized study is necessary to evaluate the role of various prokinetic agents in the performance of capsule endoscopy.