Effects of Venlafaxine, Buspirone, and Placebo on Colonic Sensorimotor Functions in Healthy Humans

Background & Aims: We have shown that venlafaxine-XR, a serotonin (5-HT) and norepinephrine reuptake inhibitor, enhanced gastric accommodation, whereas buspirone, a 5-HT(1A) receptor agonist, reduced postprandial symptoms after a fully satiating meal. Our aim was to compare the effects of venlafaxine, buspirone, and placebo on colonic sensorimotor functions in healthy adults.

Methods: In this randomized, double-blind, parallel-group, placebo-controlled trial of 60 healthy adults, we assessed the effects of oral venlafaxine, 150 mg; buspirone, 20 mg; and placebo on colonic sensorimotor functions.

Results: Venlafaxine increased colonic compliance relative to placebo; thus it decreased the intracolonic balloon pressure at half-maximum volume (P = 0.001) and altered the overall shape of the compliance curve, beta (P = 0.01). Venlafaxine also decreased fasting colonic tone (P = 0.02) and the tonic response to a meal (P = 0.003) compared with placebo; no differences in high amplitude phasic contractile events were observed. Pressure thresholds for first sensation (P = 0.1) and gas (P = 0.07) were not statistically significant with venlafaxine. The increase in pain scores per unit pressure during phasic distentions were affected by treatment (P = 0.02), with smallest changes on venlafaxine and highest on placebo. Buspirone did not significantly alter colonic compliance, tone, or sensation relative to placebo.

Conclusions: Venlafaxine alters colonic compliance and tone, and tends to reduce sensation during colonic distention in healthy humans. These data support the need for further clinical and physiologic studies of venlafaxine in colonic disorders affecting motor and possibly sensory functions.