CLONIDINE PROLONGS FENTANYL-INDUCED VENTILATORY DEPRESSION

The aim of the present study was to investigate the effect of intraven ously (i.v.) administered fentanyl and clonidine on ventilation in 12 healthy male volunteers (age 30.8+/-4.9 years) who either received fen tanyl alone (1.5 greater than or equal to mu g kg(-1)) or fentanyl (1. 5 greater than or equal to mu g kg(-1)) in combination with clonidine (3 greater than or equal to mu g kg(-1)). The effect on ventilation wa s measured with a CO2 rebreathing system. The respiratory depression c aused by fentanyl disappeared 120 min after injection. The correspondi ng slopes were 7430+/-2075 mL kPa(-1) prior to (t(0)) and 6263+/-1864 mL kPa(-1) 120 min post-application (base-line vs, t(120); P=0.106). A n impaired ventilatory response was observed during CO2 rebreathing at t(120) after the injection of fentanyl and clonidine. Before drug adm inistration, the slope of the response curves was 7700+/-2800 mL kPa(- 1), which was reduced to 5480+/-2135 mL kPa(-1) (P<0.035) at t(120). T hese data suggest a prolongation of a fentanyl-induced ventilatory dep ression when used in combination with clonidine.