Lidocaine as an analgesic for experimental pain.

The purpose of this study was to evaluate the analgesic contribution of intravenously administered lidocaine and to correlate it with blood levels of the drug. In a double-blind manner, 14 healthy male volunteers received saline solution or lidocaine, 0.2 per cent, at three increasingly greater rates of infusion on two separate days. Experimental pain was produced by means of the submaximal tourniquet-induced ischemia test of Beecher and Smith. The times to the onset of ischemic (threshold) and unbearable (tolerance) pain were recorded for three control trials to two tests for the same end points during each infusion rate. Between the two ischemic trials, while the test solution continued to be infused, venous blood samples were drawn and analyzed for lidocaine by gas chromatography. No statistically significant difference in analgesia between the control and lidocaine values for threshold or tolerance was observed at blood levels from 1 to 3 micrograms/ml. The data suggest that lidocaine at these blood levels produces sedation but not analgesia.