The FDA has added a searchable online real-time database to their Drug Safety Labeling Changes notification, which till now has been a monthly summary via email. Find the search window at http://www.accessdata.fda.gov/scripts/cder/safetylabelingchanges/ and an announcement of the service at http://www.fda.gov/Drugs/DrugSafety/ucm517519.htm . A new email notification option is also available, via a link on the search window.
