About a third of the drugs that the Food and Drug Administration deems safe and effective go on to have major safety issues years after their approval, researchers report in JAMA.

The finding lands amid pressure from lawmakers and the Trump Administration to hasten the already fast-pace of the agency’s drug reviews.

Among 222 novel therapeutics approved by the agency between 2001 and 2010, 71 (or 32 percent) had safety events arise a median of 4.2 years later. Safety events assessed in the study were marked by any of three FDA actions: withdrawing a drug entirely from the market; adding a boxed warning to a drug’s label, which is often added for life-threatening health risks; or issuing a safety communication, which is for serious, but non-life-threatening health risks.

In all, the agency withdrew three drugs*, added boxed warnings to 61, and issued safety communications for 59.

The authors of the study, led by Joseph Ross, a Yale professor of general medicine and public health policy, hope the analysis helps regulators identify features of drugs that may have hidden health risks at the time of their review. This could allow regulators to beef up reviews, increase post-market monitoring, or boost data sharing for certain drugs.

“The majority of pivotal trials that form the basis for FDA approval enroll fewer than 1,000 patients with follow-up of six months or less, which may make it challenging to identify uncommon or long-term serious safety risks,” Ross and his colleagues note. “The high frequency of post-market safety events highlights the need for continuous monitoring of the safety of novel therapeutics throughout their life cycle.”