Highlights
- •EMLA caused significant reductions in capsaicin-induced pain compared with placebo.
- •EMLA enhanced capsaicin-induced superficial blood perfusion.
- •Capsaicin reduced the neurogenic flare induced by histamine compared with EMLA.
- •Topical analgesic pretreatment does not interfere with capsaicin desensitization.
Abstract
To prevent pain associated with 8% capsaicin application, pretreatment with local
anesthetics, such as EMLA (eutectic mixture of lidocaine 2.5% and prilocaine 2.5%),
is considered an option. However, there is contradicting evidence regarding the effects
of local analgesia on capsaicin-induced desensitization. In session 1, 2 skin areas
in each forearm of 24 healthy volunteers were randomized to 2-hour pretreatment with
EMLA/placebo cream. After pretreatment, 8% capsaicin patches were applied for 3 hours
in 1 placebo and 1 EMLA pretreated area, obtaining the following four areas: Capsaicin + EMLA,
Capsaicin + Placebo, EMLA alone, and Placebo. Pain intensity scores were assessed
during the 3-hour application of capsaicin. Warmth detection, heat pain sensitivity,
and microvascular reactivity were measured after the removal of capsaicin. After 24
hours, in session 2, all tests were repeated followed by histamine application in
each area to examine itch intensity and neurogenic flare.
Overall, EMLA caused significant reductions in capsaicin-induced pain compared with
placebo (P= .007) and enhanced the capsaicin-induced increase in superficial blood perfusion
immediately after the 3-hour capsaicin application (P< .01). Regardless of pretreatment, capsaicin induced heat hyperalgesia immediately
after the application (P< .001). Twenty-four hours post application, heat pain sensitivity was normalized.
However, WDT increased significantly (P< .001). Capsaicin tended to reduce the itch intensity and significantly reduced the
neurogenic flare (P< .05) induced by histamine compared with EMLA alone. The findings suggest that pretreatment
with topical analgesic cream reduces application site pain without interfering with
the 8% topical capsaicin-induced desensitization.
Perspective
Pretreatment with local anesthetic EMLA cream might be considered a good therapeutic
option to reduce the pain associated with 8% capsaicin application currently used
for treatment of neuropathic pain syndromes. This study also suggests the existence
of a synergistic effect of capsaicin and EMLA on the process of neurogenic inflammation.
Key Words
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Article info
Publication history
Published online: January 29, 2021
Accepted:
January 26,
2021
Received in revised form:
November 24,
2020
Received:
August 3,
2020
Footnotes
Disclosures: Center for Neuroplasticity and Pain (CNAP) is supported by the Danish National Research Foundation (DNRF121). The authors have no conflict of interest to report.
Statement of exclusivity: The data included in the present paper have not been published elsewhere.
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Copyright
© 2021 by United States Association for the Study of Pain, Inc.
