Comparison of cooling and EMLA to reduce the burning pain during capsaicin 8% patch application: a randomized, double-blind, placebo-controlled study.
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.
Department of Anaesthesia, General Intensive Care and Pain Management, Medical University of Vienna, Vienna, Austria Institute of Neurology, Medical University of Vienna, Vienna, Austria Section for Clinical Biometrics, Medical University of Vienna, Vienna, Austria.
Erich
E
Knolle
Markus
M
Zadrazil
Gabor Geza
GG
Kovacs
Stephanie
S
Medwed
Gisela
G
Scharbert
Michael
M
Schemper
D000328:Adult; D002211:Capsaicin / Q000008:administration & dosage / Q000009:adverse effects*; D017679:Cryotherapy / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage*; D000077442:Lidocaine, Prilocaine Drug Combination; D008297:Male; D009824:Ointments / Q000008:administration & dosage; D010146:Pain / Q000175:diagnosis* / Q000503:physiopathology; D059408:Pain Management / Q000379:methods*; D010147:Pain Measurement / Q000379:methods*; D011318:Prilocaine / Q000008:administration & dosage*; D057968:Transdermal Patch / Q000009:adverse effects; D055815:Young Adult
D000077442:Lidocaine, Prilocaine Drug Combination; D009824:Ointments; D011318:Prilocaine; D008012:Lidocaine; D002211:Capsaicin
Capsaicin; Cooling; EMLA; Epidermal nerve fiber density; TRPV1; Topical