Levothyroxine vs Brand-Name

I vaguely remembered a comment from our endocrine teacher about not putting our patients on generic levothyroxine for hypothyroidism and that we should always opt for a brand name if the patient could afford it -- but the exact reason why had escaped me. I was recently presented with a situation in which I needed to make the call - generic vs brand - so I did some research and spoke to an endocrinologist. These are the main points that I came up with...

1. For tight control of TSH, use a brand name (which brand isn't important)
2. Tight control is particularly important in pregnant women, those looking to get pregnant, and those with h/o goiter or thyroid cancer
3. Once you pick a brand, try to stick to the same brand-name each month
4. The problem with generic levothyroxine is that the manufacturers producing the drug are variable and there are many companies moving in and out of the market so it is difficult to get the SAME generic pill each month from the pharmacy
5. If your pt can only afford generic, encourage them to take a photo of the pills that they get from the pharmacy - if they ever pick up their Rx and the pills look different then they should contact you to schedule thyroid blood work check in 5-6 weeks since the new generic could vary as much as 12.5%. If they are receiving the same generic pill each month, you should schedule normal follow ups. The bottom line is that each time they get a new generic pill from a new manufacturer, they should be re-tested.

This becomes important because many primary care providers Rx the generic because they believe that it isn't any different from brand names - and in most cases they are completely right. Ibuprofen vs Advil - no real noticeable clinical difference. The thyroid, however, is extremely sensitive and even the slightest variation from generic #1 to generic #2 can make someone's TSH impossible to tightly control and may even make them thyroid toxic.

When I presented this to several PCPs, it was received with a lot of skepticism. The first question they all asked was "Who did the study, the drug companies?" A great question to ask. The answer is... in addition to drug company studies... there have been independent studies and results have been examined by the FDA, Endocrinologist Societies (world-wide), and the Thyroid Association - all are in agreement about the results. There is a ppt available describing the results of these studies. They show the bioequivalence of generic vs brand, but also demonstrate the vast variability between generic manufacturers.

If you are looking for a quick 1 page break down of this subject - check out the following: Hennessey JV. Levothyroxine dosage and the limitations of current bioequivalence standards