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Thread: Half-lives, AIs and PCT

  1. #1

    Default Half-lives, AIs and PCT

    There has been recent discussion on this topic, and I thought more might be beneficial. The biological half-life or elimination half life of a substance is the time it takes for a substance (for example a metabolite, drug, signalling molecule, radioactive nuclide, or other substance) to lose half of its pharmacologic, physiologic, or radiologic activity, as per the MeSH definition. In a medical context, half-life may also describe the time it takes for the blood plasma concentration of a substance to halve ("plasma half-life") its steady-state. The relationship between the biological and plasma half-lives of a substance can be complex, due to factors including accumulation in tissues, active metabolites, and receptor interactions.

    Let's say that the half-life of Testosterone Enanthate is 14 days. (It may or may not be). This means that if you injected 500mg, then 14 days later, you would still have 250mg. It does not mean that 14 days after that you would have 0mg.

    Imagine that you have a 1 liter container. You fill it with 500ml orange juice and 500ml water. You make a very small hole in the bottom, so that over the course of 14 days 500ml leaks out. At the end of 14 days, there will be 250ml each of water and juice. Add 500ml water and wait 14 days. Now you will have 125ml juice and 275ml water. Add 500ml water and wait 14 days. Now you will have 62.5ml juice and 437.5ml water. Add 500ml water and wait 14 days. You will now have 31.25ml juice and 467.75ml water. Top off with 500ml water and wait 14 days. Now after 5 half-lives, or 70 days, you are down to 15.625ml juice.

    So after one 1/2, you are down to 50%, after 2x1/2, 25%. Then 12-1/2%, 6-1/4%. So it take 4 half-lives to be 94% clear. After 5 half-lives, you are 97% clear and this is when your blood and urine are considered "clean. So you can see that it also takes 4 or 5 half-lives to achieve a "steady-state" concentration. That is, for it to be eliminated as fast as it is building up.

    I am going to present a simplistic model, close enough for illustrative purposes. Lets say 500 mg week Test E and a two week half-life, with once a week injections.

    After one week you will inject 500mg (Injection #2), still having 375mg left from Injection#1(#1). After two weeks you will inject 500mg (#3), still having 250mg from (#1), and 375 from (#2). Three weeks = 500mg (#4) + 375mg (#3), 250mg (#2), 188mg (#1). Four weeks = 500mg (#5) + 375 (#4)+250(#3)+188(#2)+125(#1). So you see, after 2 half-lives, Injection #1 is @ 25%. By the time we get to week 10, or 5 half-lives we have 500+375+250+188+125+93+62+46+31+24+16(or 15.625 actually). You now have 1,710mg and will keep this "steady state" as long as you continue this dosing. You can see why the long esters start to "kick in" after several weeks. (You could always front-load with a couple grams a week the first two weeks.)

    So, whenever you stop, you will have 1,710mg in your body. two weeks after that you will have 855mg. After 4 weeks, 427.25mg. After 6 weeks, 214mg test still hanging around. After two months you will still have over 100mg test E and this is more than "normal".

    I hope this makes it more clear as to why an AI ran during PCT makes sense. And why merely blocking all this estrogen with a SERM such as nolva could conceivably lead to a rebound if discontinued too soon, and why some folks get gyno post-cycle. Personally, I feel the half-life of test E is probably closer to 10 days, but that would just mean it takes 50 days instead of 70 to build up to the steady state, and 50 days instead of 70 to be 97% clear. Either way, you're still talking supra-physiological levels well into PCT and beyond.

    It also suggests to me that one could continue to sustain a higher volume training-wise, if that's what they were doing on-cycle, as you will still have considerable cortisol blockage for a good 3-4 weeks post-cycle with a long ester. After that I would decrease training volume to avoid a cortisol rebound eating at your gains.
    Last edited by StrappingYoungLad; 06-18-2010 at 12:49 AM.

  2. #2

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    I should add that actually, the above numbers should be reduced by 28% in the case of enanthate due to the weight of the ester. There are actually only 360mg free testosterone in 500mg of testosterone enanthate. So your actual steady state amount of free test in the above example would be 1,231mg, reducing to just over 300mg free test in 2 half-lives following cessation.
    Last edited by StrappingYoungLad; 06-18-2010 at 03:50 AM.

  3. #3
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    that was like porn for my brain, sexy examples SYL we deff/ needed that to be cleared up.

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    Awesome!!!! I highly enjoyed this thread!!! Very easy read and simple!!! Thanks SYL it answered a question I've been pondering about lately!!! I'm wondering if it can be put as a sticky?!?!?
    26
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  5. #5

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    Quote Originally Posted by littleman7 View Post
    Awesome!!!! I highly enjoyed this thread!!! Very easy read and simple!!! Thanks SYL it answered a question I've been pondering about lately!!! I'm wondering if it can be put as a sticky?!?!?
    Sticking it is probably a good idea, as it is a confusing subject. I think I'll ask permission first though.

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    Yes it is...I think it will help alot of noobs understand the process of pct better and more clearly.
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    Default Well Done StrappingYoungLad

    Very well done StrappingYoungLad!
    -SMASH-

    Once we've said "can't", have we not made it so?

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    after reading this I'm worried about dosing so big...so i'm going to start a new thread with some different questions.

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    I seriously didn't know what half life meant before I landed in here. Thanks a ton for the information.

  10. #10
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    This article covers the half-life's of the most commonly used steroids, esters and ancillary compounds.

    Oral steroids Drug Active half-life
    Anadrol / Anapolan50 (oxymetholone) 8 to 9 hours
    Anavar (oxandrolone) 9 hours
    Dianabol (methandrostenolone, methandienone) 4.5 to 6 hours
    Methyltestosterone 4 days
    Winstrol (stanozolol)
    (tablets or depot taken orally) 9 hours




    Depot steroids Drug Active half-life
    Deca-durabolin (Nandrolone decanate) 15 days
    Equipoise 14 days
    Finaject (trenbolone acetate) 3 days
    Primobolan (methenolone enanthate) 10.5 days
    Sustanon or Omnadren 15 to 18 days
    Testosterone Cypionate 12 days
    Testosterone Enanthate 10.5 days
    Testosterone Propionate 2 days
    Testosterone Suspension 1 day
    * Winstrol (stanozolol) 1 day


    *Winstrol depot does not actually possess a classical half-life because it is un-esterified. Instead, the microcrystals dissolve slowly. Once they have all dissolved levels of the drug fall very rapidly. It is still an important consideration, and we have included it with a half-life of one day.



    Steroid esters Drug Active half-life
    Formate 1.5 days
    Acetate 3 days
    Propionate 2 days
    Phenylpropionate 4.5 days
    Butyrate 6 days
    Valerate 7.5 days
    Hexanoate 9 days
    Caproate 9 days
    Isocaproate 9 days
    Heptanoate 10.5 days
    Enanthate 10.5 days
    Octanoate 12 days
    Cypionate 12 days
    Nonanoate 13.5 days
    Decanoate 15 days
    Undecanoate 16.5 days




    Ancillaries Drug Active half-life
    Arimidex 3 days
    Clenbuterol 1.5 days
    Clomid 5 days
    Cytadren 6 hours
    Ephedrine 6 hours
    T3 10 hours


    A practical example is if one was to inject 100mg of testosterone propionate and allow blood levels to peak. In 4.5 days time (half-life duration from the above tables) and providing no other injections had taken place, the level would be reduced to 50mg. Again, a further 4.5 days down the line and levels would have dropped to 25mg, and the value keeps halving every 4.5 days.

    Weights
    Here is a list of testosterone and nandrolone esters by weight that I found recently. This should be helpfull in trying to determine how much actual steroid is delivered. For example, there is 70mg of testosterone per 100mg of testosterone enanthate. Naturally, the shorter the ester, the more bang-for-your-buck, so to speak.


    Testosterone Base: 100mg

    Testosterone Acetate: 83mg

    Testosterone Propionate: 80mg

    Testosterone Isocaproate: 72mg

    Testosterone Enanthate: 70mg

    Testosterone Cypionate: 69mg

    Testosterone Phenylpropionate: 66mg

    Testosterone Decanoate: 62mg

    Testosterone Undecanoate: 61mg



    Nandrolone Base: 100mg

    Nandrolone Cypionate: 69mg

    Nandrolone Phenylpropionate: 63mg

    Nandrolone Decanoate: 62mg

    Nandrolone Undecylenate: 60mg

    Nandrolone Laurate: 56mg
    Last edited by shovelhed82; 04-24-2011 at 07:53 PM.

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