The optimum concentration for epidural fentanyl. A randomised, double-blind comparison with and without 1:200 000 adrenaline

A randomised, double-blind study comparing a variety of different concentrations of fentanyl with and without 1:200 000 adrenaline is described. It was shown that the quality and duration of analgesia with epidural fentanyl was concentration-dependent below 10 micrograms/ml, but that the addition of adrenaline abolished this phenomenon. The rate of failure to achieve any analgesia was very high with the more dilute solutions, but adrenaline reversed this problem. In general the incidences of side effects were related to the concentrations of fentanyl used and apart from itching, the incidences of these side effects were reduced by the addition of adrenaline.