Background: The treatment of painful diabetic polyneuropathy (DPN) is often inadequate and frequently limited by the systemic adverse effects of medications, necessitating the evaluation of novel treatments. Objective: To evaluate the effectiveness, tolerability, and impact on quality of life of the 5% lidocaine patch in painful diabetic polyneuropathy.

No abstract

The lidocaine patch 5% appeared well tolerated and potentially effective in the management of painful idiopathic distal sensory polyneuropathy. Idiopathic distal sensory polyneuropathy is an appropriate patient population for the conduct of clinical trials of neuropathic pain therapies.

Although acute pain in patients with herpes zoster can be severe and has a substantial impact on health-related quality of life, there have been no randomized clinical trials of oral medications specifically for its ongoing treatment. A randomized clinical trial was conducted in which 87 subjects >or=50 years of age with herpes zoster within 6 calendar days of rash onset and with worst pain in the past 24h >or=3 on a 0-10 rating scale initiated 7 days of treatment with famciclovir in combination with 28 days of treatment with either controlled-release (CR) oxycodone, gabapentin, or placebo. Subjects were evaluated for adverse effects of treatment, acute pain, and health-related quality of life. The results showed that CR-oxycodone and gabapentin were generally safe and were associated with adverse events that reflect well-known effects of these medications. Discontinuing participation in the trial, primarily associated with constipation, occurred more frequently in subjects randomized to CR-oxycodone (27.6%) compared with placebo (6.9%). Treatment with CR-oxycodone reduced the mean worst pain over days 1-8 (p=0.01) and days 1-14 (p=0.02) relative to placebo but not throughout the entire 28-day treatment period as pain resolved in most subjects. Gabapentin did not provide significantly greater pain relief than placebo, although the data for the first week were consistent with a modest benefit. By demonstrating that CR-oxycodone is safe, generally adequately tolerated, and appears to have efficacy for relieving acute pain, the results of this clinical trial provide a foundation for evidence-based treatment for acute pain in herpes zoster.

Predictors of response to neuropathic pain treatment in patients with painful distal sensory neuropathies are lacking. The 5% lidocaine patch is believed to exert its effects on neuropathic pain via a local stabilizing effect on cutaneous sensory afferents. As such, it provides a model to assess whether the status of epidermal innervation as determined by skin biopsy or quantitative sensory testing (QST) of small-and large-diameter sensory afferents might serve as predictors of response to topical, locally active treatment. In this study we assessed associations between epidermal nerve fiber (ENF) densities, sensory nerve conduction studies (NCS), QST, and response to a 5% lidocaine patch in patients with painful distal sensory neuropathies. We observed no association between distal leg epidermal and subepidermal innervation and response to the lidocaine patch. Several patients with complete loss of distal leg ENF showed a response to the lidocaine patch. Similarly we observed no consistent association between treatment response and QST for vibration, cooling, warm, heat-pain, and cold-pain thresholds, or distal sensory NCS. Thus, distal-leg skin biopsy, QST, and sensory NCS cannot be used to identify patients with painful polyneuropathy likely to respond to a lidocaine patch in clinical practice. Further studies are required to clarify precisely the mechanism and site of action of the lidocaine patch in patients with peripheral neuropathic pain.