Additional old_XXXXXXtaxonomy_term__field_XXX Tables after upgrading
Not sure there is an automatic way to do this, a manual way would be to use:

echo "Show tables;" | drush @alias sql-cli | grep old &gt; drop_tables.sql


Edit the tables.txt file and add drop table and a ; after each table name.  Each line should look like:

drop table old_XXXXXXXtaxonomy_term__field_XXXX;


Backup you database in case Murphy come's around and do:

drush @alias sql-cli &lt; drop_tables.sql


That will remove them from the DB.

Alternative way to do it via a GUI would be to use MySQL Workbench and drop them thru the interface.