Drug manufacturers are required to warn you of the side effects their product could cause, and this information is most typically transferred to you by your physician or pharmacist. It is the drug manufacturer's responsibility to make this information known to medical professionals. Any new information obtained about a product's side effects must also be communicated to a physician. Just because a certain reaction to medication might be rare, this does not mean a manufacturing company cannot warn consumers about it.
Some drugs are given a "black box" warning, which highlights the serious, sometimes fatal, effects drugs could cause patients. The FDA's Adverse Event Reporting System and Office of Surveillance and Epidemiology evaluate the postmarket safety data of medicines and determine which medications be given the "black box" warning. Some "black box" labels are given at the time the drug is approved.
A study found that 40% of patients in the U.S. were prescribed one "black box" medication within a 30-month period. Pharmacists should be cautious and warn patients about "black box" labeled medications. Physicians should also be aware of those side effects.