Trial Outcomes & Findings for Ethnic Differences in Response to Topical Capsaicin: A Psychophysical Study on Healthy Subjects (NCT NCT00655811)

Last Updated: 2018-09-10

Results Overview

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.

Recruitment status

COMPLETED

Study phase

PHASE4

Target enrollment

40 participants

Primary outcome timeframe

1 day

Results posted on

2018-09-10

Participant Flow

Participant milestones

Participant milestones
Measure	Capsaicin and Placebo 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.
Overall Study STARTED	40
Overall Study COMPLETED	40
Overall Study NOT COMPLETED	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

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

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Capsaicin and Placebo n=40 Participants 0.1% Topical Capsaicin cream was appled to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.
Age, Categorical <=18 years	0 Participants n=5 Participants
Age, Categorical Between 18 and 65 years	40 Participants n=5 Participants
Age, Categorical >=65 years	0 Participants n=5 Participants
Sex: Female, Male Female	20 Participants n=5 Participants
Sex: Female, Male Male	20 Participants n=5 Participants
Race/Ethnicity, Customized African Americans	10 Participants n=5 Participants
Race/Ethnicity, Customized Caucasians	10 Participants n=5 Participants
Race/Ethnicity, Customized East Asians	10 Participants n=5 Participants
Race/Ethnicity, Customized Hispanic	10 Participants n=5 Participants
Region of Enrollment United States	40 Participants n=5 Participants

PRIMARY outcome

Timeframe: 1 day

Outcome measures

Outcome measures
Measure	African Americans n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	Caucasians n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	East Asians n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	Hispanics n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.
Ethnic Differences in Burning Pain Induced by Topical Capsaicin Capsaicin	0.81 units on a scale Standard Error 0.68	4.07 units on a scale Standard Error 1.61	17.05 units on a scale Standard Error 5.80	13.3 units on a scale Standard Error 4.67
Ethnic Differences in Burning Pain Induced by Topical Capsaicin Placebo	0 units on a scale Standard Error 0	0 units on a scale Standard Error 0	0 units on a scale Standard Error 0	0 units on a scale Standard Error 0

SECONDARY outcome

Timeframe: 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.

Outcome measures

Outcome measures
Measure	African Americans n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	Caucasians n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	East Asians n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	Hispanics n=10 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.
Ethnic Differences on the Effects of Topical Capsaicin on Thermal Sensory Thermal Thresholds Heat pain detection threshold change	-2.11 Change in degrees Celsius Standard Error 1.12	-6.10 Change in degrees Celsius Standard Error 1.36	-5.01 Change in degrees Celsius Standard Error 1.09	-7.24 Change in degrees Celsius Standard Error 0.57
Ethnic Differences on the Effects of Topical Capsaicin on Thermal Sensory Thermal Thresholds Warmth sensation threshold change	2.36 Change in degrees Celsius Standard Error 0.93	-0.68 Change in degrees Celsius Standard Error 0.68	0.56 Change in degrees Celsius Standard Error .059	-3.15 Change in degrees Celsius Standard Error 0.93

SECONDARY outcome

Timeframe: 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.

Outcome measures

Outcome measures
Measure	African Americans n=40 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	Caucasians n=40 Participants 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	East Asians 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.	Hispanics 0.1% Topical Capsaicin cream was applied to one forearm and a placebo moisturizing cream with no active ingredient (Cetaphil; Galderma Laboratories LP, Fort Worth, TX, U.S.A.) was applied to the other forearm. A volume of 0·3 mL cream was applied in a thin layer of virtually equal thickness, on a 4 × 4 cm area, around midline. The creams were applied at a 40-min interval in a random order to minimize an order effect. The creams were randomized for right and left arm application.
The Difference in Burning/Pain Sensation Ratings Between the Capsaicin or Placebo Application.	8.81 units on a scale Standard Deviation 7.63	0 units on a scale Standard Deviation 0	—	—

Adverse Events

Capsaicin

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Placebo

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Gil Yosipovitch, MD, Professor

University of Miami

Phone: 305-243-5121

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place