Double-blind Trial of Mannitol Cream to Block the Effect of Capsaicin Cream


Capsaicin is a TRPV1 (transient receptor potential vanilloid 1) agonist, causing pain upon application. The investigators wish to determine whether mannitol blocks the effect of capsaicin application. As both cream bases are identical and mannitol addition is the only difference between the creams, if the mannitol cream is more effective in blocking the effect of capsaicin on the TRPV1 (transient receptor potential vanilloid 1) receptor, the investigators will have established that mannitol down-regulates or blocks the TRPV1 (transient receptor potential vanilloid 1) receptor.

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Basic Science
    • Masking: Triple (Participant, Care Provider, Outcomes Assessor)
  • Study Primary Completion Date: January 2014

Detailed Description

Capsaicin cream, which stimulates the TRPV1 (transient receptor potential vanilloid 1) receptor, causing a burning sensation, will be applied to both halves of the upper lip until a burning sensation with 8/10 intensity on an NRS (Visual Analog Scale) scale is experienced or five minutes have elapsed. Following this, the capsaicin cream will be wiped off and 30% mannitol in vehicle cream ( isopropyl palmitate, caprylic capric triglyceride, propylene glycol, ceteareth 20, cetearyl alcohol, glyceryl stearate, polyethylene glycol 100 stearate, dimethicone, octyldodecanol, lecithin, ethylhexyl glycerin and phenoxy ethanol) will be applied to one half of the upper lip, and vehicle cream alone will be applied to the other half. Cream assignment will be randomized and neither the subject nor the person applying the cream will know which half upper lip has which cream. Every minute for 10 minutes, the heat sensation felt in each half upper lip will be measured, using a visual scale from 0 to 10. A repeated measures analysis of variance will compare the NRS (Visual Analog Scale) scores from the 30% mannitol cream, to the NRS (Visual Analog Scale)scores from the vehicle cream. Significance will be accepted if P less than .05.


  • Drug: 30% Mannitol in vehicle cream
    • applied to one half of the upper lip following removal of capsaicin cream.
  • Drug: vehicle cream
    • application to the other half of the upper lip following capsaicin cream removal

Arms, Groups and Cohorts

  • Active Comparator: Mannitol in vehicle cream
    • Once the capsaicin has been removed, .2 mL of 30% mannitol in vehicle cream will be applied to one half of the upper lip and kept there for 10 minutes.
  • Placebo Comparator: Vehicle Cream
    • Once the capsaicin has been removed, .2 mL of vehicle cream will be applied to the other half of the upper lip and kept there for 10 minutes.

Clinical Trial Outcome Measures

Primary Measures

  • NRS heat score, once per minute
    • Time Frame: 15 minutes per subject
    • Every minute after capsaicin cream application, subject will indicate NRS (numerical rating scale)heat score. When the score has reached 8/10 or after five minutes, the cream will be removed. The time needed to reach 8/10 heat score and the heat score achieved, or the score at five minutes will be recorded. Following application of the test creams, NRS (Visual Analog Scale) heat scores will be recorded once per minute for each side for 10 minutes.

Secondary Measures

  • Side effects of capsaicin cream on upper lip
    • Time Frame: One hour
    • The subject will be observed for redness, swelling, or other side effects following the capsaicin cream application. These side effects will be recorded

Participating in This Clinical Trial

Inclusion Criteria

  • Age between 19 and 80 years Exclusion Criteria:

  • Diet containing capsaicin (Cayenne pepper, capsicum) (spicy foods), more than once a week. – Meal containing capsaicin (spicy foods) within 5 days prior to the experiment. – Any lesion, cracking, cold sore or abrasion on the lips – Inability to tolerate capsaicin containing "spicy foods" – Wearing lipstick or lip balm on the upper lip – Inability to fill out an NRS pain scale – Use of painkilling medication, within 24 hours of the study. – Allergy to any of the ingredients of the creams, or to mannitol – History of contact or allergic dermatitis – Pregnant or nursing women

Gender Eligibility: All

Minimum Age: 19 Years

Maximum Age: 80 Years

Are Healthy Volunteers Accepted: Accepts Healthy Volunteers

Investigator Details

  • Lead Sponsor
    • University of British Columbia
  • Provider of Information About this Clinical Study
    • Principal Investigator: Helene Bertrand, Clinical instructor Department of Family Practice – University of British Columbia
  • Overall Official(s)
    • Helene Bertrand, MD, CM, CCFP, Principal Investigator, Department of family practice, University of British Columbia


Ngom PI, Dubray C, Woda A, Dallel R. A human oral capsaicin pain model to assess topical anesthetic-analgesic drugs. Neurosci Lett. 2001 Dec 28;316(3):149-52. doi: 10.1016/s0304-3940(01)02401-6.

Boudreau SA, Wang K, Svensson P, Sessle BJ, Arendt-Nielsen L. Vascular and psychophysical effects of topical capsaicin application to orofacial tissues. J Orofac Pain. 2009 Summer;23(3):253-64.

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