2005N-0137 Levothyroxine Sodium Therapeutic Equivalence; Notice of Public Meeting
FDA Comment Number : EC5
Submitter : Dr. Helena Rodbard Date & Time: 05/26/2005 01:05:03
Organization : Private Practice Endocrinology
Category : Health Professional
Issue Areas/Comments
I am writing as a Board Certified Endocrinologist, in private practice for more than 25 years, with training at NIH, Washington Hospital Center, George Washington University and appointments at Georgetown University.
I am writing to offer my experience with the treatment of patients with generic versions of L-thyroxine. I have found there to be clinically significant variability between generic and branded L-thyroxine, and particularly difficult is the variation between different manufacturers of generic T4. Thus, when a pharmacist or health plan change the source of their generic T4, there can be and often are wide swings in the patients clinical status - as directly observed by me, and as documented with measurements of serum T4, free T4, and especially TSH. In my view, the generics are a major source of hazzard to the community - since patients who are euthyroid on the branded T4, or on one of the generics - when switched to a generic of another source - result in the patient becoming either hyperthyroid or euthyroid. Clearly there are differences - as much as two-fold, in the effective potency/bioavailability/ pharmacodynamics of T4 from different sources. I subscribe to the thoughtful appraisals of AACE, ACE,the Endocrine Society, and the American Thyroid Association.
As an aside - I see similar findings with generics for other classes of medications as well, e.g. transdermal estrogens. I have seen more than a two- fold difference in the bio-potency of transdermal estrogens, between a branded product and a generic - resulting in major side effects and very likely, an increased risk for breast cancer.

The problems with the genrics are this: generics are supposed to save money. But the net result, due to the need for more frequent checking of T4 levels and especially TSH levels, and the need for more frequent office visits to monitor the patients status any time after a pharmacist or someone might have changed the source of the T4 in a prescription -- is an increase in the total cost of care. Thus we are paying more - and getting increased risks.

Please feel free to contact me should you have any questions.