If you're using Patch Management 7.0+ , then you can do the following:
Select all downloaded bulletins from Patch Remediation Center's All software bulletins report, right-click and select Disable. Then, go to Manage - Jobs and Tasks - System Jobs and Tasks - Software - Patch Management - Check Software Update Package Integrity. Select 'Delete updates from the file system that are no longer in use?' checkbox and start the task; it should remove all previously disabled updates.