Relation of etidocaine and bupivacaine toxicity to rate of infusion in rhesus monkeys.

The relationship between infusion rate of etidocaine and bupivacaine and central nervous system toxicity was studied in three rhesus monkeys. Increasing the infusion rate from 0.5 to 2.0 mg/kg.min-1 decreased the seizure dosage of etidocaine but had no effect on that of bupivacaine. Arterial plasma concentrations of etidocaine and bupivacaine that induced electrical seizure activity increased as the infusion rate was increased from 0.5 to 1.0 mg/kg. min-1. A plasma decay study in a fourth animal demonstrated that etidocaine decayed more rapidly than did bupivacaine. These results suggest that the rate of administration of these agents is important in determining central nervous system toxicity.