Utility of the heated lidocaine/tetracaine patch in the treatment of pain associated with shoulder impingement syndrome: a pilot study.

Introduction: Pain control is an important first step in the treatment of shoulder impingement syndrome (SIS) because fear of pain must be removed as an obstacle to participation in an appropriate physical therapy program.

Methods: Adult patients with SIS-associated pain of at least 2 weeks' duration and who had an average pain score of ≥4 on the zero- to ten-point Numeric Pain Rating Scale were eligible to enroll in this 2-week pilot study. Patients were treated with the heated lidocaine/tetracaine (70 mg/70 mg) patch (HLT patch) placed over the site of shoulder tenderness each morning and evening for a period of 2 to 4 hours. Average and worst pain during the previous 24 hours and shoulder range of motion were assessed at baseline and on Day 14. Results were expressed as change and percent change from baseline to Day 14. This pilot study was not powered for rigorous statistical analysis.

Results: Twenty patients (seven male, 13 female; average age 51.2 ± 10.8 years [mean ± standard deviation]) enrolled in this study, and 18 patients completed the protocol. The mean average pain score at baseline was 5.5 ± 1.1 (range 4 to 8). In the per-protocol population, average and worst pain scores declined by 2.4 ± 2.0 and 3.7 ± 2.7 points, respectively. Two-thirds of the patients demonstrated a clinically meaningful ≥30% decline in average pain score, and half of the patients demonstrated a ≥50% decline in average pain score. Shoulder internal rotation increased by 29.7° ± 21.8° and abduction increased by 40.0° ± 44.2°. Application-site erythema was reported by ten patients at some time during the study.

Conclusion: Patients treated with the HLT patch for 14 days demonstrated clinically meaningful improvement in pain intensity and range of motion. Further controlled research is necessary to characterize the efficacy and tolerability of the HLT patch in the treatment of SIS.