Ethnic Differences in Response to Topical Capsaicin: A Psychophysical Study on Healthy Subjects

Phase 4

Completed

Brief Summary: The purpose of this research is to study how people respond differently to capsaicin in different racial groups and the effect it has on your pain levels. Capsaicin is a natural product made from hot chili peppers that is useful for treating the itch symptoms of skin disease.

Detailed Description: To comprehensively evaluate the ethnic differences in response to topical capsaicin and its effect on thermal sensory thresholds.

Recruitment & Eligibility

Inclusion Criteria

Adult men and women who are between 18 and 50 years of age.
Subjects must be in general good health with no skin disease, disease state or physical condition which would impair evaluation of pain perception or which would increase their health risk by study participation as determined by the investigators.
Women of childbearing potential will be required to have a negative pregnancy test in order to enroll in the study.

Exclusion Criteria

Adults over age 50.
Children less than 18 years of age.
Unable to complete the required measures.
Diagnosis of diseases that would affect the measurement of pain perception.
Currently enrolled in any investigational study in which the subject is receiving any type of drug, biologic, or non-drug therapy and subjects undergoing treatment with another investigational drug or approved therapy for investigational use within 30 days prior to study participation.
Use of oral analgesic or other medications known to interfere with pain perception in the week prior to the study.
Use of emollient on the forearms on the day of the study visit.
Use of medicated topical preparations on the forearms for the week prior to the study.
Known history of neuropathy causing diseases such as uremia.
Known history of uncontrolled thyroid disease.
Known history of diabetes mellitus.
Allergy to capsaicin.
Pregnant women.

Arm && Interventions

Group	Intervention	Description
Placebo moisturizing cream	Placebo moisturizing cream	Placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) to the opposite forearm.
Capsaicin	Capsaicin	Capsaicin 0.1% cream application to the volar side of forearm.

Primary Outcome Measures

Name	Time	Method
Ethnic Differences in Burning Pain Induced by Topical Capsaicin	1 day	The primary endpoint is to test the burning pain effect of topical capsaicin by using an continuous visual analog scale (CoVAS) intensity scale as an outcome measure. Participants will rate burning pain intensity after topical capsaicin application. The burning or pain sensation intensity was recorded continuously on a 100-mm COVAS (0, no sensation to 100, maximum, strongest imaginable pain sensation). The subjects were also asked to indicate whether they experienced any nonpainful sensation.

Secondary Outcome Measures

Name	Time	Method
The Difference in Burning/Pain Sensation Ratings Between the Capsaicin or Placebo Application.	1 day	This secondary outcome is to see if subjects rated burning/pain differently between the topical capsaicin or placebo application. Participants will rate burning/pain intensity after topical capsaicin and placebo application. The burning/pain sensation intensity was recorded continuously on a 100-mm COVAS (0, no sensation to 100, maximum, strongest imaginable burning/pain sensation). The subjects were also asked to indicate whether they experienced any non-burning/-painful sensation.
Ethnic Differences on the Effects of Topical Capsaicin on Thermal Sensory Thermal Thresholds	1 day	A secondary endpoint is to see if topical capsaicin has an effect on warm and heat pain thresholds. Quantitative thermosensory testing was carried out using the Medoc TSA 2001 (Medoc Ltd). The probe baseline temperature was 32 °C and the contact area was 12 cm2. The probe warmed the skin surface at a linear rate of 0·4 °C per second, up to a cut-off of 50 °C. Thermal thresholds were measured in the following order: warmth sensation threshold was measured followed by heat pain detection threshold; each of them was determined four times by the ascending method of limits.