A medication used to treat hypothyroidism has been voluntarily recalled due to quality concerns.

Westminster Pharmaceuticals, LLC has instructed wholesalers to stop distributing specific products labeled "Levothyroxine and Liothyronine (Thyroid Tablets, USP)," according to an August 9 release. Levothyroxine and Liothyronine are synthetic hormones contained in the thyroid tablets.

The voluntary national recall alert says there have been no "adverse events" associated with the recalled products. It says patients should continue taking the drugs.

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"Because these products may be used in the treatment of serious medical conditions, patients taking the recalled medicines should continue taking their medicine until they have a replacement product," the release says.

More than 4.5 percent of the U.S. population over the age of 12 suffers from an underactive thyroid or hypothyroidism, according to the National Library of Medicine's MedlinePlus.

The release instructs patients to speak with their physician before discontinuing use of the medicine.

The recall follows a June 22 warning letter from the Food & Drug Administration to a Chinese pharmaceutical company which manufactured active ingredients in the recalled drug. The letter cited a number of failures, including ones relating to "established standards of quality and purity."

The recall alert says issues cited in that warning letter "could represent the possibility of risk being introduced into the manufacturing process."

A full list of recalled products is available from the FDA.

Patients with questions or information about an issue relating to the recalled products can contact Westminster at: 888-354-9939.