Lidocaine as an Analgesic for Experimental Pain

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Abstract
The analgesic contribution of i.v. administered lidocaine was studied and correlated with blood levels of the drug. In a double-blind study, 14 healthy male volunteers received saline solution or lidocaine, 0.2%, at 3 increasingly greater rates of infusion on 2 separate days. Experimental pain was produced by 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 3 control trials to 2 tests for the same end points during each infusion rate. Between the 2 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 seen at blood levels of 1-3 .mu.g/ml. Lidocaine at these blood levels apparently produces sedation but not analgesia.