Low-dose intravenous erythromycin: effects on postprandial and fasting motility of the small bowel

Background: Erythromycin is a motilin agonist and its effects on gastrointe stinal motility are dependent on both dose and whether it is administered d uring the postprandial or fasting state. Aim: To study the motility response of the small bowel to a low dose of int ravenous erythromycin after meal intake and during fasting. Methods: Eighteen healthy subjects with mean age of 25 years were studied b y small bowel manometry. Erythromycin was administered intravenously (0.75 mg per kg body weight) during 20 min in the postprandial (n = 9) and the fa sting state (n = 9), and the motility response was recorded. Results: Erythromycin significantly reduced the frequency of propagated con tractions (P < 0.001) and the amplitude of contractions (P < 0.02) in the s mall bowel during established postprandial motility. During the fasting sta te, erythromycin invariably initiated a phase III-like activity, which was similar to the spontaneous nocturnal phase III and migrated significantly m ore slowly than the diurnal phase III (P < 0.01). Conclusions: A low dose of erythromycin administered intravenously during t he postprandial state significantly inhibits small bowel motility, whereas administration during the fasting state initiates a phase III resembling th e nocturnal rather than the diurnal phase III. These effects of erythromyci n may indicate interference with vagal pathways. Due to its inhibitory effe cts, the clinical use of erythromycin in patients with hypomotility should be reconsidered, and the potential usefulness of these effects in patients with exaggerated intestinal motility deserves further attention.