OSX Mavericks has no PEAR (and your Drush is probably gone too).
Install PEAR -
sudo php -d detect_unicode=0 /usr/lib/php/install-pear-nozlib.phar
Install Drush -
sudo pear channel-discover pear.drush.org
sudo pear install drush/drush
Run Drush as root once so Drush installs Console::Getopt etc.
sudo drush help