Comparison of cooling and EMLA to reduce the burning pain during capsaicin 8%
patch application: a randomized, double-blind, placebo-controlled study.
Author(s): Knolle E(1), Zadrazil M, Kovacs GG, Medwed S, Scharbert G, Schemper M.
Affiliation(s): Author information:
(1)Department of Anaesthesia, General Intensive Care and Pain Management, Medical
University of Vienna, Vienna, Austria. Electronic address:
erich.knolle@meduniwien.ac.at.
Publication date & source: 2013, Pain. , 154(12):2729-36
Topical capsaicin 8% was developed for the treatment of peripheral neuropathic
pain. The pain reduction is associated with a reversible reduction of epidermal
nerve fiber density (ENFD). During its application, topical capsaicin 8% provokes
distinct pain. In a randomized, double-blind study analyzed with a block
factorial analysis of variance, we tested whether cooling the skin would result
in reliable prevention of the application pain without inhibiting reduction of
ENFD. A capsaicin 8% patch was cut into 4 quarters and 2 each were applied for 1
hour on the anterior thighs of 12 healthy volunteers. A randomization scheme
provided for 1 of the application sites of each thigh to be pretreated with EMLA
and the other with placebo, whereas both application sites of 1 thigh, also
randomly selected, were cooled by cool packs, resulting in a site temperature of
20°C during the entire treatment period. The maximum pain level given for the
cooled sites (visual analogue scale [VAS] 1.3 ± 1.4) proved to be significantly
lower than for the non-cooled sites (VAS 7.5 ± 1.9) (P < .0001). In contrast,
there was no significant difference in application pain between the sites
pretreated with EMLA or with placebo (VAS 4.1 ± 3.6 vs 4.8 ± 3.5, P = .1084). At
all application sites, ENFD was significantly reduced by 8.0 ± 2.8 (ENF/mm ± SD,
P < .0001), that is, 70%, with no significant differences between the sites with
the different experimental conditions. In conclusion, cooling the skin to 20°C
reliably prevents the pain from capsaicin 8% patch application, whereas EMLA does
not. ENFD reduction is not inhibited by cooling.
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