Metalink note 271855.1 has a script aqcoalesce.sql
To quote from the note
The procedure performs the following operations relating to AQ objects

alter table AQ$_ < QUEUE_TABLE_NAME > _X coalesce;
where X=I (dequeue), T (time_manager), and H (history) IOTS for multi-consumer queue tables and

alter index AQ$_ < QUEUE_TABLE_NAME > _Y rebuild;
where Y=I (dequeue), and T (time-manager) indexes for single-consumer queue tables