Evaluation of the analgesic effect and urinary excretion of systemic bupivacaine in man.

Bupivacaine was infused intravenously into healthy volunteers to assess its analgesic effect. In a double-blind manner, 11 male subjects received, on separate days, saline solution or 0.1% bupivacaine, at three rates of infusion. Experimental pain was produced by the tourniquet-induced ischemia test. Times to onset of ischemic pain (threshold) and unbearable pain (tolerance) were compared. Venous blood samples were analyzed for levels of bupivacaine and its metabolite, pipecolyxylidine, by gas chromatography. No significant difference in pain threshold or tolerance was found following control and bupivacaine infusion. In the 72-hour postinfusion urine collection period, only 0.7% of the infused dose was recovered as unmetabolized bupivacaine, with 4.8% recovered as pipecolyxylidine. Systemic blood levels of bupivacaine achieved during regional anesthesia did not produce analgesia in this model.