FDA moves to ensure thyroid drug potency

The US Food and Drug Administration says that it is tightening potency specifications for levothyroxine sodium, a key component of drugs used to treat underactive thyroid-related conditions, in an effort to ensure such products maintain therapeutic efficacy throughout their shelf life. The agency said that, from now on, levothyroxine sodium-based drugs must meet potency requirements in a narrow 95% to 105% range of their labeling claims for the full duration of their availability.

The FDA explained that it was moving in response to concerns that the quality of drugs containing the ingredient, which it estimates are used by over 13 million patients, may deteriorate prior to shelf life expiration. The agency said that manufacturers of affected products, such as Abbott Laboratories which makes Synthroid, have two years to comply with the revised specification, and added that its action is consistent with the recommendations of its joint advisory committee.