Lidoderm Studied for New Applications
An estimated 25 million Americans experience acute pain as a result of injury or surgery, and an estimated 50 million Americans suffer from chronic pain according to Joseph S. Gimbel, M.D., Arizona Research Center, Phoenix, Ariz., the principal investigator in two of the pilot studies. The most common chronic pain condition is back pain, which affects an estimated 36 million Americans. Pain can be relieved or greatly eased with proper pain management; however, most sufferers go untreated, under-treated, or improperly treated. Untreated pain can have significant physical, psychological and financial consequences by impacting daily functioning and quality of life. Pain costs Americans an estimated $100 billion each year due to lost wages and healthcare expenses. Pain is the leading cause of medically related work absenteeism, resulting in more than 50 million lost workdays each year. Researchers are continually evaluating and developing new pharmacologic interventions that may improve the quality of life for patients suffering with chronic pain. The following preliminary results show promising potential in mitigating pain in certain chronic pain syndromes.
Lidoderm® is a targeted topical analgesic patch that is applied directly to intact skin. Lidoderm® (lidocaine patch 5%) is currently FDA-approved for relief of pain associated with post-herpetic neuralgia, a chronic pain that can result from nerve damage by the herpes zoster virus, commonly referred to as shingles. Lidoderm® produces an analgesic effect by the penetration of lidocaine from the patch into intact skin, without complete loss of sensation or numbness. Lidoderm® should only be applied to intact skin. Reactions to Lidoderm® are generally mild and transient. During or immediately after treatment with Lidoderm®, the skin at the site of treatment may develop erythema or edema or may be the locus of abnormal sensation. Lidoderm® is contraindicated in patients with a known history of sensitivity to local anesthetics of the amide type, or to any other component product. The FDA-approved dosing for Lidoderm® is up to three patches applied for up to 12 hours within a 24-hour period. However, the safety and efficacy of Lidoderm® have not been established when used with dosing regimens above three patches per day. In clinical practice, a vast majority of patients are administered one Lidoderm® patch per day.
While the preliminary data presented in the following sections suggest that Lidoderm® (lidocaine patch 5%) may provide pain relief and/or impact pain interference with quality of life in the four chronic pain conditions studied (post-herpetic neuralgia, diabetic neuropathy, osteoarthritis, and low back pain), Lidoderm is not currently FDA-approved for treatment of these conditions and the safety and efficacy of Lidoderm® have not been established. Experimental use of Lidoderm for these chronic pain syndromes at this stage of the FDA approval process is “off-label” and warrants extra caution during investigative use.
Postherpetic Neuralgia, Diabetic Neuralgia, and Low Back Pain
The first study was an open-label, multicenter, two-week pilot study designed to assess the impact of Lidoderm® (up to four patches every 24 hours) in patients with postherpetic neuralgia (PHN) (n=11), diabetic neuropathy (n=49), or low back pain (n=47) and who experienced a partial response to their current analgesic regimen that included gabapentin (Neurontin®). Using the Brief Pain Inventory (see Appendix A for source information) to assess pain interference with quality of life, the investigators found that the addition of Lidoderm® reduced pain interference with most measures in the PHN group (general activity, mood, normal work, sleep, enjoyment of life) and in all measures in the diabetic neuropathy and low back pain groups (general activity, mood, walking ability, normal work, relations with other people, sleep, enjoyment of life). In this study, Lidoderm® was well-tolerated, with relatively few clinical adverse events, most of which were mild to moderate. The most frequently reported treatment-related adverse events were somnolence and headache (2.8%).
Low Back Pain
In a separate nonrandomized, prospective, open-label, two-week pilot study of nonradicular acute/subacute (<3 months; n=20), short-term chronic (3-12 months; n=33), and long-term chronic (>12 months; n=76) low back pain sufferers, patients were treated for two weeks with up to four Lidoderm® patches every 24 hours to the area of maximal peripheral pain while continuing their current analgesic regimen without dosage adjustment. Using the Brief Pain Inventory to assess pain intensity and relief, investigators found that Lidoderm® produced significant improvements in pain intensity in all groups for worst pain, average pain, and pain right now, as well as significant improvements in least pain and pain relief for acute/subacute and long-term chronic groups. All groups showed significant reductions in the Brief Pain Inventory composite score for pain interference with quality of life and the Beck Depression Inventory score (see Appendix A for source information). The lidocaine patch 5% was well tolerated, with mild-to-moderate application site reactions (e.g., erythema, irritation, edema, paresthesia, puritis) being the most commonly reported treatment-related adverse event (13%). There were no serious systemic adverse events or drug-drug interactions related to treatment.
Painful diabetic neuropathy, which occurs in 20-24% of patients with diabetes, includes a variety of painful sensations such as tingling or burning of the lower extremities, either with or without allodynia (pain caused by normally non-painful stimuli such as rough clothing or light touch). In a prospective, nonrandomized, three-week, open-label pilot study of 56 diabetic neuropathy patients, up to four Lidoderm® patches were applied for 18 hours per day to areas of maximal peripheral neuropathic pain. Patients continued their current analgesic medication, without dosing adjustment. The results suggest that Lidoderm® produced significant improvements in pain intensity, pain relief, and pain interference with quality of life both in patients with allodynia (n=19) and without allodynia (n=37). No systemic adverse events or drug-drug interactions related to the lidocaine patch 5% were reported. The most frequently reported adverse event was mild application site burning (10%).