Objective: To determine the impact of the lidocaine patch 5% on pain qualities associated with chronic pain from postherpetic neuralgia (PHN), painful diabetic neuropathy (DN), and low-back pain (LBP), using the Neuropathic Pain Scale (NPS).
Patients and methods: Patients with PHN, painful DN, and LBP were enrolled if they had partial response to gabapentin-containing analgesic regimens and if they reported moderate-to-severe pain on the NPS at study enrollment. Eligible patients were included in an open-label, non-randomized, prospective, 2-week study across 7 clinical trial sites in the United States. The lidocaine patch 5% was applied to the area of maximal pain, using no more than a total of 4 patches changed every 24 h. Patients were maintained on their other analgesic regimens with no dose adjustment or additions allowed. Treatment effect was measured by change from baseline to Week 2 in 4 composite measures of the NPS: NPS-10, NPS-4, NPS-8, and NPS-non-allodynia. Safety was assessed by adverse events (AEs), dermal assessment of application site(s), and skin sensory testing.
Results: In the combined patient population (n = 77), 2 weeks of treatment with the lidocaine patch 5% significantly improved all 4 composite measures (p < 0.01). In the subgroup analyses, the lidocaine patch 5% demonstrated numerical advantage for all 4 NPS composite measures for the PHN patients (n = 8), and significantly improved all 4 composite measures for the painful DN patients (n = 41; p < 0.001) and LBP patients (n = 28; p < or = 0.005). Overall, 8 patients (10%) experienced mild-to-moderate treatment-related AEs.
Conclusions: The lidocaine patch 5% effectively reduces the intensity of all common pain qualities in patients with moderate-to-severe chronic pain resulting from PHN, painful DN, or LBP. Treatment is well tolerated in combination with other analgesic regimens, with no reports of serious AEs or adverse drug interactions. Assessment scales such as the NPS may offer the possibility to differentiate between various pain states and to assess treatment outcomes for various pain qualities associated with a given pain state.