Low potential of dobutamine and dopexamine to block intestinal peristalsisas compared with other catecholamines

Objective: Catecholamines are frequently used in critically ill patients to restore stable hemodynamics and to improve organ perfusion. One effect of short-term or long-term administration of catecholamines may be inhibition of propulsive motility in the intestine. We therefore analyzed the effect o f dopexamine, dobutamine, and dopamine on ileal peristalsis and compared th eir action with that of epinephrine and norepinephrine, which have long bee n known to suppress intestinal peristalsis. Design: In vitro study on excised guinea pig ileum segments. Setting: Laboratory for experimental studies at the University. Subjects. Isolated guinea pig ileum. Interventions: Segments of ileum excised from guinea pigs were mounted in a tissue bath in Krebs-Henseleit solution and bubbled with 95% oxygen/5% CO2 . Luminal perfusion with the same solution was performed at a rate of 0.35 mL/min. The bath temperature was kept at 36.5 degrees C. Peristalsis was re corded via changes in the intraluminal pressure. The drugs under investigat ion (dopamine, epinephrine, norepinephrine, dobutamine, and dopexamine) wer e added to the tissue bath. Measurements and Main Results: Low concentrations of each catecholamine, ex cept epinephrine, caused a decrease in the pressure threshold, which reflec ts a stimulatory effect on peristalsis. Higher catecholamine concentrations caused a concentration-related increase in the threshold, cumulating in a complete block of peristalsis. The rank order of inhibitory potency was epi nephrine > norepinephrine > dopamine > dobutamine similar to dopexamine. Do butamine and dopexamine were about 500-fold less active than epinephrine in suppressing peristalsis. Conclusions: This study shows that dobutamine and dopexamine have the least potential to block propulsive motility in the intestine, whereas epinephri ne demonstrates the most adverse inhibitory effect. Because at low concentr ations dobutamine and dopexamine even stimulate peristalsis, these drugs ap pear to be superior compared with other catecholamines with regard to their direct effects on intestinal motility.