This is a question that comes up occasionally from thyroid patients.
If someone is on one type of T3 (or even NDT), and it is being taken in several divided doses per day, but the patient needs to change brands for whatever reason, what is the best way to go about this?
Please do not wait until one type of medication runs out, before trying out the new brand! It is definitely a bad idea to accumulate any of a new brand, without testing it to see if it is going to work well. Also, swapping all doses at once is not advisable, as the brands may have different strengths and may even have unwanted side effects.
The advice I always give to thyroid patients is to pick the last dose of the day, and to swap this dose to the equivalent dose size in the new brand. Try this for a week or two, and fine-tune the new brand dose size until it really does perform as well as the current medication – in terms of signs and symptoms. If the new brand works well for the last dose of the day, then apply the same process, one by one, to your other T3 doses. If all goes well, and if you have plenty of your original brand left, then switch back to the original brand and dose sizes to use them up first as their expiry dates are likely to be earlier. Save your new brand with longer expiry dates for later, when your original medication runs out.
It is possible however, that the new medication might not work as well as the original brand. So, giving it at least a few weeks to assess it, is sensible. If the new brand is problematic (perhaps due to a binder or filler), then go back to your pharmacist, or doctor, and tell them quickly, so they can give you a different brand. This is why it is essential to begin testing any new brand quickly, even though you may have plenty of the original medication left. Waiting and using up the original whilst accumulating some of the newer brand of medication is not sensible, and would likely make your doctor and pharmacist upset, if you have to take back a lot of the new brand because you had delayed testing it.
The main thing to do is to start early, well before your old medication has run out.
Note also: the absorption of a new brand might be different between different people. So, if someone tells you that this particular brand needs a 22.5 mcg dose compared to the current brand which needs a 20 mcg dose, this may be different for you. You have to use the process I am suggesting above if you want to do this correctly.
I hope this helps.
Best wishes,
Paul
