What causes differences in generic levothyroxine?

July 11, 2008

Hi, I had an episode of sleep apnoea last night. This was the 1st

one since I started medication and I had been getting them 2 to 3

times a week in the months before then. Today I have woken up

feeling really hypothyroid, fuzzy achey and swollen. I feel like

I've been kicked in the chest and am a bit wobbly.

I suspect I'm still undermedicated at 100mcg but read today's

Shomon article about the symptoms of overmedication out of interest.

m

One paragraph struck me as particularly relevant to my situation:

" If you are taking generic levothyroxine (which most doctors do not

recommend), in your last refill, you may have gotten a more potent

batch. Even the slight change of potency from one refill to the

next, particularly from one manufacturer of generic levothyoxine to

another, can be enough to push you into hyperthyroidism. "

Well, I don't get a say in what brand is prescribed, they ONLY do

generic here. My 1st and current pills are actavis branded. In

between I was prescribed Teva brand and coincidentally developed

sore itchy swollen eyes and burning skin plus allergic sneezing.

This appeared to improve with the actavis (which I started, having

set aside the last pills in my teva pack). Yesterday I took the last

teva pills to see whether I genuinely had a problem with them. My

eyes are VERY itchy this morning and my skin hurts. I'm going to

avoid that brand in future, travelling from chemist to chemist if I

have to - so a result of sorts! Strange thing is the filler

ingredients are the same for both brands.

But I don't understand how the potency of levothyroxine can vary

from batch to batch. It is synthetic so I would have thought its

potency would be controllable. I also don't understand how the

inconsistent-potency argument is used against prescribing animal-

sourced thyoxine but NOT against synthetic levothyroxine. What

causes the potency variations anyway?

Tracey

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