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Topical Capsaicin 0.075 Percent Best Choice For Double Blinded Studies: Presented at WCP
By Peggy Peck
Special to DG News
SAN DIEGO, CA -- August 21, 2002 -- Results of a study comparing the irritant effects of topical capsaicin at various concentrations indicate that 0.075 percent maintains efficacy while minimising skin irritations.
Based on these findings, the researchers recommend that double blinded studies should use the 0.075 percent cream concentration.
Lead investigator William Ackerman, MD, of Pain Medicine, Arkansas Specialty Care, in Little Rock, Arkansas, United States, said that for general clinical practice 0.125 percent capsaicin "demonstrates the greatest efficacy and is only rarely associated with patient discomfort."
Dr. Ackerman, who presented his findings August 20th at the 10th World Congress on Pain, said that it has been difficult to use capsaicin in double blind trials because "patients complain of skin irritation and often fail to comply [with treatment]".
His team compared the incidence of skin irritation, pain and pruritus with different commercial concentrations of topical capsaicin cream.
After obtaining Institutional Review Board approval and informed consent from patients, they enrolled 15 adult volunteers. In a double-blinded fashion, they used a template and an applicator to apply a placebo cream and four concentrations of capsaicin cream (0.025 percent, 0.075 percent, 0.125 percent and 0.25 percent) to different linear spots on the right forearm of each subject.
They assessed pruritus scores and visual analog score (VAS) at baseline and again at five-minute intervals for 60 minutes. Laser Doppler fluxmetric studies were done to determine skin perfusion on both forearms with the left forearm as a control at baseline and every 15 minutes for 60 minutes. Skin perfusion changes were expressed as the percent differences between the study and control limbs.
Subjects who received 0.25 percent capsaicin all had significant pain, pruritus and increased skin blood flow. Patients in the 0.125 percent group had discomfort (VAS <3) and two patients had a significant increase in tissue blood flow. There were no reports of skin discomfort in the 0.075 capsaicin group, he said.
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