Low potential of dobutamine and dopexamine to block intestinal peristalsis as 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 of dopexamine, dobutamine, and dopamine on ileal peristalsis and compared their action with that of epinephrine and norepinephrine, which have long been 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 recorded via changes in the intraluminal pressure. The drugs under investigation (dopamine, epinephrine, norepinephrine, dobutamine, and dopexamine) were added to the tissue bath. Measurements and Main Results: Low concentrations of each catecholamine, except epinephrine, caused a decrease in the pressure threshold, which reflects 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 epinephrine > norepinephrine > dopamine > dobutamine similar to dopexamine. Dobutamine 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 epinephrine demonstrates the most adverse inhibitory effect. Because at low concentrations dobutamine and dopexamine even stimulate peristalsis, these drugs appear to be superior compared with other catecholamines with regard to their direct effects on intestinal motility.