Presented at the 2012 AAPM Annual Meeting « Back

Does Mechanical Pain Sensitivity Differentiate Responders to Capsaicin 8% Patch Treatment?

Burkhard Gustorff, MD, burkhard.gustorff@weinkav.at¹, Herwig Kloimstein, MD², Nicole Hacker³, S. Maier⁴, Chris D. Poole, PhD⁵, Rudolf Likar, MD⁴, (1) Department of Anaesthesia, Intensive Care, and Pain Medicine, Vienna, Austria, (2) Anaesthetist, Vienna, Austria, (3) Medical University of Vienna, Vienna, Austria, (4) LKH Klagenfurt, Klagenfurt, Austria, (5) Pharmatelligence, Cardiff, South Glamorgan, Wales, UK

Introduction: Capsaicin 8% patch (QTZ) is a novel treatment for peripheral neuropathic pain. Identifying characteristics associated with treatment response could improve treatment targeting. Methods: Thirty-one hospital outpatients received QTZ over a 12-month period starting in April 2010. Somatosensory perception of both treated and contralateral untreated areas was tested with quantitative sensory testing (QST) prior to treatment, after 24 hours, 1 week, 1 month, and 3 months. Responders were those who at 1 month had a ≥30% reduction in numerical pain rating scale (NPRS) average pain from baseline. Mechanical pain sensitivity (MPS) was determined by estimating the stimulus response function (SRF) to fixed stimulus intensities (8 to 512 mN) using a punctate probe. Results: Fifteen patients completed all observations, and eight responded to treatment (53%). At baseline, responders exhibited increased MPS over non-responders as characterized by SRF with higher intercept (+16.521 vs. +1.4849; Figure 1) and shallow slope (0.0498 vs. 0.1122). At 1 month, responders showed normalization of nociceptive function (reduced intercept, +6.2159; increased slope, 0.0848; p = 0.055). Conclusion: In this small sample, responders to QTZ treatment were characterized by baseline hyperalgesia to weak pinprick stimuli which resolved after treatment. Mechanical pain sensitivity testing could identify patients more likely to respond to QTZ treatment.

Funding: Unrestricted research grant from Astellas Pharma Europe Ltd.

Figure 1. Mechanical pain sensitivity stimulus response functions for responders and nonresponders to capsaicin 8% patch treatment as measured as baseline (BL) and 1-month (1M).