Studies on the duration of local anaesthesia: a possible mechanism for the prolonging effect of dextran on the duration of infiltration anaesthesia.

The mechanism of the prolonged effect of dextran on the duration of local anaesthesia has been studied. Using radio-active mepivacaine it was found that dextran prolonged the duration of infiltration anaesthesia in guinea-pigs by delaying the absorption of the local anaesthetic agent. Experiments in vitro indicate that molecular complexes between the local anaesthetic and dextran may be formed and it is assumed that the delayed absorption might be due to the formation of such molecular complexes. This hypothesis was strengthened by experiments in which dental infiltration anaesthesias were performed in healthy volunteers.