The Effect of Dextran on the Pharmacokinetics of Lignocaine during Epidural Anaesthesia

Abstract

The clinical significance of combining local anaesthetics with dextran is controversial. Although a number of investigators have found that dextran can prolong the action of local anaesthetics, others have not been able to demonstrate any significant change in the duration of anaesthesia. A study was carried out to investigate the effect of dextran on the pharmacokinetic behaviour of lignocaine during epidural anaesthesia in 20 adult male patients, who were randomly allocated to two treatment groups: group 1 ( n = 10) was given lignocaine – dextran; group 2 ( n = 10) was given lignocaine – saline. The results of the study demonstrated that the addition of dextran to epidural lignocaine significantly slowed systemic absorption of lignocaine as indicated by a smaller absorption rate constant, a reduced peak plasma concentration (Cmax), a delayed time to reach Cmax, and a smaller area under the concentration – time curve. The observed findings suggest that dextran reduces vascular uptake of lignocaine from epidural space and that it may prolong the duration of action. The significance of these findings on systemic toxicity, dosage and onset of action of lignocaine need to be investigated.