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Session-Order Sensitivity of TS and OA in a Capsaicin Crossover Model

NCT07625475 · Status: COMPLETED · Phase: NA · Type: INTERVENTIONAL · Enrollment: 16

Last updated 2026-06-04

No results posted yet for this study

Summary

Temporal summation (TS) and offset analgesia (OA) are widely used psychophysical endpoints in pain research that index different components of central nociceptive processing. While crossover designs are commonly used in experimental pain studies to reduce between-participant variability, the design-stability of these endpoints under repeated testing during experimental sensitisation is not well characterised. This study compared the design-stability of mechanical TS (Sumscore) and offset analgesia magnitude (OffA) in a two-period, vehicle-controlled crossover trial of capsaicin-evoked secondary hyperalgesia in healthy adults. The primary aim was methodological: to determine whether session-order effects differ between TS and OffA when these are used as outcome measures in two-period crossover designs of capsaicin-induced central sensitisation. Topical capsaicin was used as a reversible experimental intervention to create a controlled, transient state of secondary hyperalgesia rather than as a therapeutic intervention. The study informs endpoint selection in future quantitative sensory testing (QST) crossover trials.

Conditions

  • Hyperalgesia
  • Pain Perception
  • Central Nervous System Sensitization
  • Pain Threshold

Interventions

DRUG

Topical 0.075% capsaicin cream (Zostrix)

5 mL of 0.075% capsaicin cream (Zostrix; Hi-Tech Pharmacal, Amityville, NY, USA) applied to a 5 x 10 cm target region on the lateral elbow and to bilateral C5-C6 cervicothoracic dermatomes (total 15 mL). The cream was massaged into the skin by a gloved investigator until no residue was visible. Used as an experimental probe to evoke transient, reversible secondary hyperalgesia; not under therapeutic evaluation.

OTHER

Topical vehicle lotion (Lubriderm)

5 mL of inert vehicle lotion (Lubriderm; Johnson \& Johnson, Montgomery, NJ, USA) applied to the same dermatomes as the capsaicin condition (total 15 mL), using the identical preparation and massage technique. Matched to the capsaicin cream for colour and texture.

Sponsors & Collaborators

  • University of Guelph

    lead OTHER

Study Design

Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Model
CROSSOVER

Eligibility

Min Age
18 Years
Sex
ALL
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2024-05-01
Primary Completion
2025-04-30
Completion
2025-04-30

Countries

  • Canada

Study Locations

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Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT07625475 on ClinicalTrials.gov