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Ensuring Potency of Thyroid Drugs

FDA is tightening the potency specifications for levothyroxine sodium, used to treat underactive thyroid glands and other thyroid conditions, to ensure that the drug retains its potency over its entire shelf life. The shelf life is the length of time a drug can be stored before it degrades to unacceptable levels.

A healthy, functioning thyroid gland is critical to regulating a person's overall metabolic function, which impacts a host of other bodily functions.

FDA is taking this recent action in response to concerns that the drug's potency may deteriorate prior to its expiration date. The change will help improve the quality of the product so that consumers receive the level of medication needed to treat their thyroid disorders. Levothyroxine sodium products are used by over 13 million patients.

• Currently, these products are allowed a potency range of 90 to 110%. FDA is mandating that levothyroxine sodium drug products meet a 95 to 105% potency specification until their expiration date.
• The 95% lower potency specification will ensure the drugs do not degrade by more than 5% of the labeled claim before their expiration date. The 105% upper specification is appropriate to address occasional analytical testing variability.
• Manufacturers and marketers have two years to comply with the revised specification.

Consumers can also help maintain the potency of their medications by storing them in a dry place at room temperature and avoiding humid, hot environments such as bathrooms, which speed deterioration.

For More Information

Thyroid Medications: Q & A with Mary Parks, M.D.
www.fda.gov/consumer/features/thyroid010208.html

FDA Press Release
http://www.fda.gov/bbs/topics/NEWS/2007/NEW01717.html

Levothyroxine Sodium Product Information
http://www.fda.gov/cder/drug/infopage/levothyroxine/default.htm

Date Posted: October 12, 2007

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