Activation of peripheral opioid receptors has no effect on heart rate variability

Opioid receptors involved in regulating the motility of the gastrointestinal tract have been localized in both contractile and neuronal tissues. Trimebutine, a peripheral opioid receptor agonist, modulates gastrointestinal motor activity in both directions and also may act on cardiac tissue. This study investigated the effects of trimebutine in clinical doses on cardiac autonomic functions with heart rate variability. The effect of trimebutine on cardiac autonomic outflows was evaluated in 11 healthy subjects. Trimebutine (200 mg) or placebo was administered orally at random in a double-blind, cross-over manner. Continuous electrocardiography recordings were obtained before and after drug administration during three states: rest, controlled breathing, and a hand grip exercise. Heart rate variability analysis showed that there was no significant difference between subjects administered with placebo or trimebutine throughout rest, controlled breathing, or the hand grip exercise. We concluded that trimebutine, in clinical doses, has no significant effect on cardiac autonomic functions.