Safety issues arising for drugs already approved by the US Food and Drug Administration (FDA) appear to be quite common. A new study has found that for drugs approved between 2001 and 2010, nearly one in three had a postmarket safety event.

The study team defined postmarket safety events as those that lead to either withdrawal from the market due to safety concerns, a boxed warning or FDA issuance of a safety communication.

Among 222 novel therapeutics approved by the FDA during this time period, 71, or 32% were affected by a postmarket safety event, according to the study published in the journal JAMA.

“These safety risks emerge, on average, four years after approval. This means that many patients are exposed to these medications before the risks become clear,” said lead author of the study Nicholas Downing from Brigham and Women’s Hospital in Boston, Massachusetts.

The team found that three drugs had been withdrawn from the market over an average follow-up period of 11.7 years.

Boxed warnings, which are issued when new, life-threatening risks are identified, were issued for 61 drugs, including antipsychotics, SSRIs (selective serotonin reuptake inhibitors) and a class of drugs for the treatment of autoimmune disease.

Safety communications, which are issued when new, serious risks are identified, were issued for 59 drugs, including drugs for migraine, erectile dysfunction and diabetes.

There were 123 new postmarket safety events (three withdrawals, 61 boxed warnings, and 59 safety communications) affecting 71 of the 222 novel therapeutics, the researchers said.

Postmarket safety events were significantly more frequent among biologics, therapeutics indicated for the treatment of psychiatric disease, those receiving accelerated approval and those with near-regulatory deadline approval, the study said.