If you’re still sudo installing npms you should upgrade to the latest version of Node.js (which also installs npm) - it no longer requires sudo to install packages.
@jorge - you may have installed ionic to a particular directory and not globally (the -g flag) so it’s not available anywhere.
Try this:
$ npm cache clear
$ npm uninstall ionic
$ npm install ionic -g
Then the Ionic CLI should work for you anywhere.