Treatment Impact on Patient-Reported Outcomes in Peripheral Neuropathic Pain: Comparing Single Intervention With Topical High-Concentration Capsaicin to Daily Oral Pregabalin

Background: Peripheral neuropathic pain (PNP) is a complex, subjective experience affecting both physical and psychological aspects of functioning. Assessing patient-reported outcomes (PROs) beyond pain relief is important and aligns with the recommendations of IMMPACT (Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials). Moreover, PRO data are key to clinical decision-making when evaluating treatment options. However, direct comparisons between such options are scarce. High-concentration capsaicin 179 mg (8% w/w) cutaneous patch (HCCP) is applied to the skin at minimum intervals of 90 days under physician supervision; alternative recommended treatments for PNP are mostly orally administered on a daily basis. The ELEVATE study directly compared HCCP with pregabalin and found noninferior efficacy of HCCP to pregabalin in relieving pain after 8 weeks, with a significantly faster onset of action and fewer systemic side effects.

Objectives: The objective of this analysis was to compare PRO outcomes defined as secondary objectives of the ELEVATE study after a single intervention with HCCP to daily oral pregabalin for 8 weeks.

Study design: ELEVATE was an open-label, randomized (1:1) multicenter study.

Setting: The study included 92 sites in 22 countries in Europe and Asia.

Methods: Five hundred fifty-nine non-diabetic patients with PNP received a single intervention with HCCP (n = 282; 1-4 patches at baseline) or oral daily pregabalin (n = 277; 150-600 mg, 8 weeks). At baseline (Day 0) and Week 8, patients completed the following PROs in addition to the regular pain assessments: Patient Global Impression of Change (PGIC), Medical Outcomes Study Cognitive Functioning scale (MOS-Cog), Medical Outcomes Study Sleep scale (MOS-Sleep), Treatment Satisfaction Questionnaire for Medication (TSQM), and EuroQol 5-Dimensions 5-levels (EQ-5D-5L) Utility Index (EQ-UI) and Visual Analog Scale (EQ-VAS).

Results: At Week 8, 76% and 75.9% of patients on HCCP and pregabalin, respectively, reported to be very much/much/minimally improved on the PGIC. HCCP application was associated with significant improvements from baseline vs. pregabalin in MOS-Cog (mean difference: 4.28 [95% CI: 2.90-5.66]; P < 0.001), EQ-VAS (3.11 [0.30-5.92]; P = 0.030), and TSQM global satisfaction (6.74 [2.29-11.20]; P = 0.029), particularly the side-effects dimension (21.23 [17.55-24.94]; P < 0.0001). No significant differences in improvements were noted for the MOS-Sleep, TSQM convenience, and EQ-UI.

Limitations: The ELEVATE study has an open-label design, with only one comparator (pregabalin); it was limited to 8 weeks. The sample size was determined for the primary endpoint.

Conclusions: A single intervention with HCCP showed benefits vs. daily pregabalin at Week 8 on several PROs. While HCCP has been approved in the United States for PNP treatment in diabetic and PHN patients, these observations provide information on how patients perceive the effects of distinct PNP treatments. They are complementing already existing knowledge on efficacy and safety of different treatment options with data on patient preferences and may help identify the appropriate treatment option in dialogue with the patients and shared decision-making.IRB Approval: At the time of the study, the trial was approved either nationally or at site level. All approvals were granted prior to the initiation of the trial. A list of Ethics Committees that approved the trial is included as a supplemental file.

Clinical trial registration number: NCT01713426.