The peripheral opioid antagonist methylnaltrexone does not abolish the negative effects of remifentanil on swallowing and on lower esophageal sphincter pressure

Opioid analgesics may influence upper airway function, inducing swallowing problems and opioids decrease the lower esophageal sphincter (LES) pressure. In this study we investigated whether the peripheral opioid receptor antagonist methylnaltrexone could.

Methods

The study was approved by the Ethics Committee and was performed in 10 healthy volunteers, mean age 25 (21-31) years and mean body mass index 24.4 ± 5,4 kg/m². The volunteers were studied on two occasions. The LES pressure was recorded by a high-resolution solid state manometry technique (Manoscan 360, Sierra Scientific Instruments Inc, Los Angeles,CA) and the effects on swallowing were evaluated by questions at different time intervals and registered on a 4-grade scale.

After transnasal placement of the manometry catheter and 30 minutes before the remifentanil infusion, the volunteers received, in a randomized order, methylnaltrexone 0.15 mg/kg bw s.c. on one occasion and a corresponding volume of normal saline (placebo) on the other occasion. Thereafter, on both occasions, the infusion of remifentanil with a target concentration of 3 ng/ml was started and continued for 30 minutes.

Results 

Remifentanil induced swallowing problems in 7 of 10 volunteers when they had received  methylnaltrexone and in 9 of 10 volunteers when they had received placebo. The lower esophageal sphincter pressure decreased on both occasions during the Remifentanil infusion; the decrease was 6,1 ± 7.0 mmHg (p=0,03)following methylnaltrexone and 6,8 ± 5,2 mmHg (p=0.003) following placebo.

Conclusion

Remifentanil induced swallowing problems in volunteers and decreased the lower esophageal sphincter pressure. These effects were not abolished by the peripheral opioid antagonist methylnaltrexone, and are consequently not mediated by peripheral opioid receptors.