Intravenous lidocaine for neuropathic pain: a retrospective analysis of tolerability and efficacy.

OBJECTIVES: This study was designed to describe the efficacy and toxicity of intravenous (i.v.) lidocaine infusions for the treatment of neuropathic pain initially administered at a flat-rate trial dose of 500 mg over 30 minutes.

SETTING: Academic, tertiary care hospital and infusion center.

METHODS: Data were retrospectively collected and analyzed for efficacy, correlations between infusion rates with adverse effects, patterns of infusion rate adjustments, and infusion frequencies.

RESULTS: The average rate for all infusions was 9.1 mg/min. Efficacy was seen in 45 patients (65%), and all but eight patients (12%) required infusion rate reductions from the initial test rate of 16.7 mg/min due to adverse effects. Fifty-five patients experienced adverse effects, with light-headedness as the most frequently reported side effect.

CONCLUSION: The flat-dose trial used under the University of Wisconsin Health protocol for i.v. lidocaine administration did not cause serious adverse events, but few patients who responded to this trial dose tolerated subsequent infusions at the trial rate. Due to the lack of serious adverse events, administering an aggressive trial dose to elicit an analgesic response appears to be rational. If patients show a benefit from the trial dose, the need for reductions in infusion rate of subsequent doses should be anticipated.