For Drupal cached pages force url to lower case doesn't work

Working Rewrite rule to achieve this scenario in conf file

RewriteEngine on
RewriteMap lowercase int:tolower
RewriteCond $1 [A-Z]
RewriteCond $1 !\.(css|js|gz|jpe?g|gif|png)$ [NC]
RewriteRule ^/?(.*)$ /${lowercase:$1} [R=301,L]  

Reference : http://www.askapache.com/htaccess/rewrite-uppercase-lowercase.html

Thanks
anup