| abstract |
The present invention directs to provide a novel compound for treating and/or preventing pain, having excellent skin permeation and reduced skin irritation. The present invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof (R 1 : a methyl group or other like group, R 2 : a fluorine atom or other like group, R 3 : a methyl group or other like group, R 4 : a methyl group or other like group, R 5 : a methyl group or other like group) |