A randomized, controlled study comparing a lidocaine patch, a placebo patch, and anesthetic injection for treatment of trigger points in patients with myofascial pain syndrome: evaluation of pain and somatic pain thresholds

BACKGROUND: Myofascial pain syndrome (MPS), a regional pain condition caused by trigger points in muscle or muscle fascia, produces muscle pain, tenderness, and disability. The gold standard of treatment for MPS-infiltration of trigger points with anesthetic-may provoke discomfort to the patients and require medical intervention.

OBJECTIVES: This study was designed to compare the effects of a topical lidocaine patch, a placebo patch, and injection of anesthetic (infiltration) for the symptoms of MPS in terms of pain, disability, and local tissue hypersensitivity, and to determine the acceptability of the lidocaine patch to the patients.

METHODS: Patients were randomly allocated to receive 1 of 3 treatments: a lidocaine patch applied to the trigger point for 4 days (replacement every 12 hours; total daily dose, 350 mg), a placebo patch applied to the trigger point for 4 days (replacement every 12 hours), or infiltration of the trigger point with two 1-mL injections of 0.5% bupivacaine hydrochloride given 2 days apart. Treatment with the patches was double-blinded, whereas treatment with infiltration was single-blinded. The number of pain attacks, pain intensity at rest and on movement, and pain-related interference with daily activity, work activity, mood, and quality of life were recorded before, during, and after treatment using a visual analog scale (VAS). Pressure and electrical pain thresholds of the skin, subcutis, and muscle in the trigger point, target area, and a pain-free area were evaluated before starting therapy (day 1) and on days 5 and 9. A VAS was used to measure discomfort from therapy, and a diary was given to each patient to record requests for additional treatment (if needed) and adverse effects.

RESULTS: Sixty white patients (46 women and 14 men) 19 to 76 years of age were studied. Mean (SD) age was 46.88 (15.37) years, and mean (SD) weight was 69.58 (13.94) kg. Twenty patients were assigned to each treatment group. Subjective symptoms did not change with placebo, but decreased significantly with the lidocaine patch and infiltration (both, P < 0.001) relative to baseline. Pain thresholds did not vary with the placebo patch, but increased significantly with the lidocaine patch and infiltration (all, P < 0.001); effects at muscle trigger points and target areas were greater with infiltration. Discomfort from therapy was greater with infiltration than with the lidocaine patch. Only patients in the placebo group requested additional treatment (P < 0.001). No adverse events occurred in any group.

CONCLUSION: Lidocaine patches were effective in, and highly acceptable to, these patients with MPS and high tissue hypersensitivity.