Involvement of two different pathways in the motor effects of erythromycin on the gastric antrum in humans.

BACKGROUND During the interdigestive state in humans, erythromycin 40 mg induces a premature activity front that starts in the stomach, while erythromycin 200 mg induces a prolonged period of enhanced antral contractile activity. AIMS To study the involvement of a cholinergic pathway in the motor effects of erythromycin using the muscarinic antagonist atropine and the neural 5-HT1 receptor agonist sumatriptan. METHODS In 30 healthy volunteers, fasted antroduodenojejunal motor activity was studied by stationary manometry. Placebo (n = 10), atropine (15 micrograms/kg intravenous bolus plus 15 micrograms/kg/h over 30 minutes; n = 10), or sumatriptan (6 mg subcutaneously; n = 10) was administered, followed by infusion of erythromycin 40 mg or 200 mg. RESULTS After placebo, erythromycin 40 mg induced a premature activity front with gastric onset after 19.1 (1.7) minutes in all volunteers. After atropine, erythromycin 40 mg failed to induce a premature activity front during a 60 minute period in all volunteers (p < 0.001), while sumatriptan prevented the induction of a premature activity front during a 60 minute period in all but one volunteer (p < 0.005). The number of antral contractions and their mean amplitude in the 60 minutes after erythromycin 200 mg did not differ significantly after atropine or sumatriptan versus placebo. CONCLUSIONS The antral motor effects of erythromycin in humans are mediated via different pathways. The induction of a premature activity front is mediated through activation of an intrinsic cholinergic pathway, while the induction of enhanced antral contractile activity may be mediated via a pathway potentially involving activation of a muscular receptor.