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How Much T (& Dht) Does Bicalutamide Block?

Discussion in 'Antiandrogens - Propecia, Dutasteride, etc.' started by DHTcel, Jun 18, 2019.

  1. DHTcel

    Jan 27, 2019
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    First, how much does Bicalutamide increase T by?
    At doses between 10mg to 200mg, there is anywhere from a 21-73% increase in T regardless, so lets just say there is a 50% average increase in T from bicalutamide.

    How much androgens(T + DHT) does bicalutamide block?
    "sufficiently high relative concentrations of bicalutamide (1,000- fold excess) are able to completely prevent activation of the AR by androgens like DHT and testosterone and subsequent upregulation of the transcription of androgen-responsive genes and associated effects.[39][20][40][41] At steady-state, relative to the normal adult male range for testosterone levels (300–1,000 ng/dL),[42] circulating concentrations of bicalutamide at 50 mg/day are roughly 600 to 2,500 times higher and at 150 mg/day around 1,500 to 8,000 times higher than circulating testosterone levels"

    if you do the math then 50mg would reach a 1,000 fold excess for <500ng/dl of testosterone
    and 100mg would reach a 1,000 fold excess for <1000ng/dl of testosterone
    and 150mg would reach a 1,500 fold excess for <1500ng/dl of testosterone
    (this is assuming you are not using something to reduce DHT) aka using bicalutamide by itself

    What if I am using something to lower DHT? (finasteride/dutasteride)
    lets just assume someone is using dutasteride to reduce their DHT by 95% and assume that there is no DHT in the body, only T.

    Well "DHT is a potent agonist of the AR, and is in fact the most potent known endogenous ligand of the receptor. It has an affinity (Kd) of 0.25 to 0.5 nM for the human AR, which is about 2- to 3-fold higher than that of testosterone (Kd = 0.4 to 1.0 nM)"

    So we can be aggressive and assume that the Kd (affinity) of Testosterone: 0.4nM
    and the Kd (affinity) of DHT: 0.25nM.

    So if someone was using dutasteride (or finasteride) then they could use a lower dose of bicalutamide since they are only blocking T. DHT has a 2-3 fold higher binding affinity of testosterone so more bicalutamide is required to block it from the AR if DHT is not being blocked already.

    I'm on dutasteride, so how much Testosterone does bicalutamide block?
    well since we don't have to worry about DHT, we have to reapply the math on the affinity of testosterone vs dht to see how much bicalutamide is required to only block T from the AR.

    0.4nM/0.25nM=1.6 as a ratio

    so we do

    so that means

    50mg bicalutamide blocks - 800ng/dl of testosterone
    100mg bicalutamide blocks - 1,600ng/dl of testosterone
    150mg bicalutamide blocks - 2,400ng/dl of testosterone

    it is important that you do not take an SAA with bicalutamide since it will interfere with the drug (SAA's are partial agonists of the AR)

    if you use tamoxifen then there will be an additional 50% increase in T
    and if you use raloxifene there will be an additional 20% increase in T

    how I chose my dose of bicalutamide
    my total testosterone on my last blood test was 913ng/dl.
    so if I take bica my T will go up 50% and raloxifine will also increase my T by 20% (Tamoxifen increases T by 50% but Im not using that)
    so 913*1.7=1552ng/dl

    Im also on dutasteride so I can look at the second chart which shows I can take only 100mg bicalutamide.

    Hope this was informative.

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    #1 DHTcel, Jun 18, 2019
    Last edited: Jun 23, 2019

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