Safety issues frequently emerge after a drug has been introduced to the market. These concerns arise either through ongoing clinical research or adverse events reported by post-market surveillance of the drug. The FDA can act upon this information in a number of ways. It can choose to remove the drug from the market or it can issue an advisory to physicians, the strongest of which is a "black box" warning which appears on the drug label.


How they so love to trivilize... 
Examining The Impact Of FDA Safety Warnings 
 
I mean, think about it.  If they're concerned warnings aren't working, they probably aren't.....  or there's just TOO much money to be made by selfish ingrates who keep breading the masses to have slaves...