Effect of various doses of erythromycin on colonic myoelectrical activity in IBS patients

Abstract Erythromycin mimics the effects of motilin but its action on colonic motility is still controversial. The aim of this study was to evaluate the effect of intravenous infusions of various doses of erythromycin on colonic motility in patients with irritable bowel syndrome (IBS). At 09.00 hours, day 1 (D1), an intraluminal probe was introduced up to the right colon in 24 IBS patients with myoelectrical activity recorded for 48 h. Patients were randomised in three groups of eight, receiving either erythromycin 1.5, 3 or 7 mg kg−1. All were investigated as follows: at 09.00 hours, D2, fasted patients were infused with erythromycin in 30 min; at 09.00 hours, D3, glycerol 10 ml was injected intraluminally. Colonic activity was measured 30 min before the infusion started, during and 30 min after it, separately in the left and right colons, and expressed in time occupied during the recording period. Basal activity was similar in both parts of the colon. During and after erythromycin 1.5 and 3 mg kg−1, colonic activity remained unchanged. Erythromycin 7 mg kg−1 induced a moderate increase in spiking activity (long spike bursts or LSBs + 33%; migrating LSBs or MLSBs + 41%) in the right colon, no change being statistically significant; activities in the left colon were similar to basal level. During the first 30 min following glycerol injection, mean short spike burst or SSB activity did not change, mean LSB activity increased by seven fold (P = 0.014) and MLSB activity by ten fold (P = 0.023). Erythromycin at doses from 1.5 to 7 mg kg−1 failed to stimulate colonic motility in IBS patients. By contrast, response to glycerol was strong, suggesting normal colonic responsiveness. Erythromycin stimulatory effects could be limited to the upper gut at least in IBS patients.