This randomized controlled clinical study tested the clinical efficacy of the topical 5% lidocaine patch for the treatment of PHN pain. The 5% lidocaine patch was found to have a significant pain reduction effect, as represented by the lower pain intensity VAS scores and the higher category pain relief scores, when compared with the vehicle patch. Most of the patients in the study continued to take their oral agents which provided partial pain relief, and they reported that the addition of the lidocaine patch resulted in a noticeably-improved pain relief. This addictive effect of improved pain control supports the previously stated view of rational polypharmacy, that is, combining agents with different mechanisms of action are likely to be beneficial to patients with PHN.
Fig. 1 Course of mean VAS scores after application of the 5% lidocaine patches and the vehicle patch. Lidocaine patches were superior to the vehicle patch for pain reduction at the time points 12 hr, 24 hr, 48 hr and 72 hr (individual time points: p<0.001 to £>=0.015). Compared with the baseline, lidocaine patch application was superior at the times points 12 hr, 24 hr, 48 hr, and 72 hr (individual time points p < 0.001 to £=0.033). LP: 5% lidocaine patch, VP: vehicle patch.
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Fig. 2, Course of mean category pain relief scores after application of the 5% lidocaine patches and the vehicle patch. Lidocaine patch application was superior to the vehicle patch at all time points (individual time points: £<0.001 to p=0.04). LP: 5% lidocaine patch, VP: vehicle patch.