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Anyone take Anastrozole every other day?
Breast Cancer | Last Active: 2 days ago | Replies (48)Comment receiving replies
I'd like to comment on myoga's post--in particular her statement "The half life of anastrozole is 50 hours, why do we have to take it everyday? After 100 days we accumulate over 50 pills(?) in our system."
The half-life of a medication is the time it takes for half of the dose to leave the body. Suppose 1 anastrozole pill contains 1 mg. 50 hours after you take the pill, 0.5 mg is still in your body. After another 50 hours 0.25 mg is still in your body. After another 50 hours, 0.125 mg is still in your body--and so on. You take anastrozole every day, because some of it leaves your body every day. So you have to keep replenishing it to keep a constant level.
Generally, it takes about 6 half-lives for a drug to reach a steady state in the body. That steady state level for anastrozole is about 1 mg. You do **not** accumulate 50 pills worth of anastrozole in your system if you take it for 100 days.
Also, even if one AI gives you terrible side effects, a different one may not. There's no way of predicting which (if any) you'll be able to tolerate. You just have to try each one and see. Is this a good situation? I'd say "no" but right now AIs (and tamoxifen) are all we've got. A better med (Giredestrant) is in the pipeline but (as far as I know) not yet available except in a research setting.
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@peggydobbs
I agree! The reason I put 50 with a question mark because I know it’s not 50. To calculate the exact amount of the accumulated drug in your body you need to have a mathematical equation which I don’t remember since I’ve been out of college for over 40 years. I can always research to find out the exact amount. But that’s not my point! My point is that if the half life is 50 hours, then we are accumulating more medication in our body than we need to lower estrogen. The amount of medication we need depending on our body weight and it shouldn’t be one size fits all or it seems like we’re overdosed! That explains the links you posted regarding lower doses being non inferior to standard doses for AIs. By the way, taking it everyday is not keeping “constant level”, you actually accumulate as time goes on because half life is 50 hours. So the first day is 1mg, the next day would be 1mg+1mg(1-24/100) and so on, right?
I came across the article regarding the lower dose for exemestane about a year ago. Exemestane half life is 24 hours, yet taking it 3 times a week is non inferior to standard one a day. That could mean the amount of drug in one pill is more than what we need if taking daily.
I’m not advocating or encouraging lower doses, but if your body can’t handle the full dose, then you need to discuss with your doctor if lower dose is right for you. Would it be better to take lower dose than not to take it at all. Then again if I get to 70s, I would be more interested in living the rest of my life pain free. It’s a personal choice and I respect that. As far as I’m concerned we are here to support our sisters, not judging them.