Harmful drug-drug interactions for thyroid medicines identified

Thyroid drugs, which are among the most frequently prescribed medicines in the USA, may adversely interact with common over-the-counter and prescription products, consumer group Public Citizen writes in a new September posting on its WorstPills.org web site.

The effects of these interactions can include diminished effectiveness of the thyroid medication, as well as of other drugs, and life-threatening impacts on the blood's ability to clot. Doctors can prevent adverse outcomes by adjusting the dosage of the drugs and, for some of the interactions, educating patients about appropriate times, relative to each other, to take them.

In 2007 alone, says Public Citizen, doctors prescribed the thyroid medication levothyroxine to more than 75 million Americans, making it one of the most commonly-used drugs in the country. The compound, sold in the USA as Levo-T, Levoxyl, Novothyrox, Synthroid, Thyro-Tabs and Unitroid, supplements the missing or deficient thyroid hormone to prevent hypothyroidism.