Original Research

Lidocaine patch 5% for carpal tunnel syndrome: How it compares with injections: A pilot study

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Practice recommendations
  • The lidocaine patch 5% provided pain relief for mild-to-moderate carpal tunnel syndrome.
  • The lidocaine patch 5% may offer patients a noninvasive treatment option with minimal risk for drug-drug interactions or systemic side effects.
Abstract
  • Objectives: A standard treatment option for mild-to-moderate carpal tunnel syndrome (CTS) is a local injection of anesthetic-corticosteroid, but this can be painful and may cause complications. This pilot clinical trial was designed to compare the safety and efficacy of daily applications of the lidocaine patch 5% (Lidoderm) to that of a single injection of 0.5 cc lidocaine 1% plus methylprednisolone acetate (Depo-Medrol) 40 mg.
  • Methods: In this randomized, parallel-group, open-label, single-center, active-controlled, prospective pilot study, participants aged 18–75 years with clinical/electrodiagnostic evidence of CTS were randomized to receive the lidocaine patch 5% or 1 injection of 0.5 cc lidocaine 1% plus methylprednisolone acetate 40 mg. Outcome assessments included the Brief Pain Inventory (measuring pain intensity, relief, and interference with quality of life, Patient and Global Clinical Impression of Improvement, Global Assessment of Treatment Satisfaction, and safety.
  • Results: Baseline characteristics of the 40 patients randomized to treatment with the lidocaine patch 5% (n=20) or injection (n=20) were similar between groups. After 4 weeks of treatment, patients in both groups reported significant changes (P<.05) in worst pain, average pain, and pain “right now.” Composite interference scores, which are measures of how much patients’ pain interfered with quality of life, also significantly improved in both treatment groups (patch, –13.9; injection, –16.7; P<.001 vs baseline for both groups). Eighty percent of patients in the lidocaine patch group and 59% of patients who received the injection reported being “satisfied” or “very satisfied,” while investigators reported improvement in 88% of patients using the lidocaine patch and in 74% of those who received the injection. Both treatments were well tolerated, with treatment-related adverse events (AEs) reported in 3 patients in each group (15%). No systemic treatment-related AEs were observed with the lidocaine patch 5%.
  • Conclusions: This pilot trial demonstrated that the lidocaine patch 5% was efficacious in reducing pain associated with CTS and was well tolerated. The lidocaine patch 5% may offer patients with CTS effective, noninvasive treatment for the management of their symptoms. Further controlled trials are warranted.

Treatment options for carpal tunnel syndrome (CTS) include wrist splinting, oral corticosteroids, and local injections with anesthetics and corticosteroids for mild-to-moderate cases, and surgical release for severe cases.1

Injections work, but have drawbacks. Injecting a corticosteroid and local anesthetic into, or proximal to, the carpal tunnel gives significantly greater relief than oral steroids.2 In fact, a recent randomized, open-label trial demonstrated that local steroid injections may relieve CTS pain as well as, or better than, invasive surgery.3 However, corticosteroid injections are time consuming and costly. Moreover, inadvertent injections into the nerve can lead to chronic pain and long-term discomfort.4-6 Repeated injections carry the risk for needle injury to the median nerve, intratendinous injection and tendon rupture, adhesions, dysesthesias, and infection.1 Many clinicians limit the number of injections into the carpal tunnel to about 3 or 4 per year to minimize local complications and the possibility of systemic toxic side effects (eg, hyperglycemia or hypertension).7

The thinking behind a new approach. Because nonsurgical treatment options for CTS are suboptimal, new therapies are needed.8 The pain of peripheral nerve injury—eg, CTS-associated median nerve compression—may result from changes in voltage-gated sodium channels in the injured afferents and their uninjured neighbors.9 These changes may have a profound impact on neuronal excitability, causing abnormal sodium channel expression, spontaneous and ectopic sodium channel discharge, and neuropathic pain.10 Pharmacologically blocking these channels and the processes underlying their changes may be the most efficient way of selectively eliminating the associated pain.10 Because lidocaine is believed to stabilize the sodium channels in damaged afferent neurons,11 the lidocaine patch 5% may be an appropriate treatment option for patients with CTS.

Related evidence. The lidocaine patch 5% is indicated for treating pain associated with postherpetic neuralgia and can be used with minimal risk of drug-drug interactions.12 Recent literature suggests that the lidocaine patch 5% may relieve pain associated with multiple types of peripheral neuropathies13,14; therefore, patients with CTS may also benefit from this modality.

The formulation relieves localized pain and may be particularly appropriate for patients who are awaiting surgery or wish to limit their exposure to corticosteroids, such as those with diabetes, heart disease, or hypertension. Though there are anecdotal reports of success with topical lidocaine patches for CTS, its efficacy and safety have not been evaluated in randomized trials or documented in published literature.

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