Lidocaine patch 5% for carpal tunnel syndrome: How it compares with injections: A pilot study
Focus of our pilot study. To investigate the role of topical lidocaine in relieving pain or functional impairment caused by persistent or recurrent CTS, we conducted a randomized pilot trial comparing the safety and efficacy of daily applications of the lidocaine patch 5% (Lidoderm) with the efficacy and safety of a single injection of 0.5 cc lidocaine 1% and methylprednisolone acetate (Depo-Medrol) 40 mg in patients with mild-to-moderate CTS.
Methods
Participants and design
This trial was a 4-week, randomized, parallel-group, open-label, single-center, active-controlled, prospective pilot study conducted in the United States. The Ethical Review Committee, Inc, located in Kansas City, Kansas, reviewed and approved the study. Patients 18 to 75 years with clinical and electrodiagnostic evidence of CTS were randomly assigned to receive the lidocaine patch 5% or a single injection of 0.5 cc lidocaine 1% and methylprednisolone acetate 40 mg.
Inclusion criteria. Electrodiagnostic evidence of CTS included a median motor nerve distal latency more than 4.10 m sec or a difference of more than 1 m sec between the median and ulnar sensory latencies when recorded with the fourth finger.15 Patients also were required to have persistent or recurrent CTS as defined by the presence of pain, paresthesias, or positive Phalen’s or Tinel’s signs. We enrolled patients who met the eligibility criteria, gave consent, and attended 1 of 2 treatment centers (a family practice clinic or a physical medicine clinic) between November 2003 and May 2004. Patients were not recruited from the general population and were not given incentives to participate other than free treatment. Patients were enrolled after providing written informed consent.
Exclusion criteria. Patients were excluded from the study if they had peripheral neuropathy of any origin other than CTS, carpal tunnel injection in the study limb within the previous 8 weeks, carpal tunnel surgical release of the study limb within the previous 6 months, concomitant cervical radiculopathy, anatomic abnormalities of the wrist or hand, median nerve injury from trauma, upper motor neuron disturbance causing spastic or nonspastic paresis or plegia of the affected limb, or thenar weakness sufficient to require tendon transfer to support thumb opposition.
Other exclusion criteria were concomitant use of the lidocaine patch 5% for any other condition, participation in a clinical trial within the previous 30 days, and pregnancy. Women who were breastfeeding or were of childbearing potential who were not using a reliable form of contraception were also excluded, as were patients with thenar atrophy or significantly prolonged median motor nerve distal latencies indicative of severe CTS.
Interventions
Using a predefined randomization sequence, patients were assigned in strict consecutive order to 1 of 2 treatments: daily applications of the lidocaine patch 5% or a single injection of 0.5 cc lidocaine 1% plus Depo-Medrol 40 mg. Patients assigned to the lidocaine patch 5% were instructed to cover the volar aspect of the wrist—using up to 3 patches per day, covering a surface area of up to 420 cm2, and as much of the painful area as possible—for 24 hours a day. Patients were also instructed to change the patches each day for 4 weeks and were allowed to cut the patch to size. Just one investigator (SN), who has more than 10 years experience giving corticosteroid injections into the carpal tunnel, performed the injections on each patient in this group.
Routine concomitant use of analgesic medications for CTS was not permitted; however, patients were allowed to use analgesics as needed for acute episodes of pain. Patients were asked at each study visit about concomitant medication use, including other analgesics. Patients using splints at the time of randomization were allowed to continue using them, but patients were not permitted to begin using splints during the trial. Adherence among patients randomized to the patch was evaluated by patch counts.
Outcome assessments
Patients were evaluated at baseline, at 2 interim points (Week 1 and Week 2), and at the study’s conclusion (Week 4). The Brief Pain Inventory (BPI) was used at each evaluation to assess pain intensity, pain relief, and pain interference with various domains of quality of life (QOL).16 These domains included general activity, mood, walking ability, normal work, relationships with other people, sleep, and enjoyment of life. Global assessment of pain relief and satisfaction, using the Patient and Global Clinical Impression of Improvement (CGI-I) and the Global Assessment of Treatment Satisfaction (PGAS), was also evaluated. The Patient and Global Clinical Impression of Change are 7-point scales in which patients and clinicians rate changes in overall status since beginning study medication. The Global Assessment of Treatment Satisfaction measure assesses patient responses to the question “Overall, how satisfied are you with your treatment?” Results are rated on a 5-point scale. Safety and tolerability were assessed via adverse event monitoring.
