Anavar and Caffeine, revisited
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Many of you (you know who you are) either are or should be aware of the fascinating Portuguese study on how caffeine affects oral oxandrolone concentration.
https://www.adop.pt/media/4114/Oxandrolone_excretion_effect_of_caffeine_dosing_.pdf
The basic design of the study was as follows: A 400 microgram (0.4mg) dose of oxandrolone was administered to a "regular drinker of caffeine", reported to be equivalent to around 3 espressos a day. Urine was collected for 70 hours following.
4 days subsequent to the initial administration, 400 micrograms of the same was co-administered with 300 mg caffeine.
The results are displayed below:
Clearly, when caffeine was co-administered with oxandrolone, the rate of excretion (measured in ng/min of urine) of oxandrolone was significantly greater than that when caffeine was not co-administered.
The quantity represented, however, is perhaps not as informative as we would like. After all, ng/min is a bit of a strange unit.
Ideally, we would also have the total amount of oxandrolone excreted under the two conditions
While the study authors did not provide such a figure, I estimated it by hand from the above data using trapezoidal approximation.
The total micrograms of oxandrolone excreted without caffeine was approx. 2.8 mcg, or about 0.7% of the oral dose by weight.
The total micrograms excreted with caffeine was approximately 90 micrograms, or about 22% of the oral dose by weight.
Now, the study also measured the amount of the major metabolite of oxandrolone, epioxandrolone.
Oxandrolone is only negligibly metabolized to epioxandrolone, however, so I did not calculate the AUC for that metabolite.
The study authors conclude the study by saying that, not only did the maximum concentration of oxandrolone in the urine for caffeine+oxandrolone almost 20x the maximum in the oxandrolone only trial, but max amount of epioxandrolone was only 15x that for oxandrolone solo.
Therefore, in the caffeine + oxandrolone trial, not only was far, far more oxandrolone excreted, proportionally less of what was excreteted was epioxandrolone
These remarkable findings raise the question: how do we explain these results, and what are their implications?
Well, the fact that there was approximately 30 times the amount of oxandrolone excreted when it was administered with caffeine suggests that caffeine massively increased the absorption of oxandrolone.
And indeed, caffeine is a known inhibitor of P-glycoprotein transporter, which normally causes oxandrolone to be retained in the gut and not absorbed.
The 30x increase, however, is puzzling. It seems unlikely that PGP alone could explain that
Perhaps the decreased proportion of epioxandrolone produced can be explained by caffeine inhibiting CPY enzymes slightly.
We need, however, a satisfying explanation for why this 30x increase was observed
It could not be that oxandrolone was somehow retained more in the body when it was administered alone. That is not how oral steroid metabolism works. We should assume that the difference in amount excreted is explained by a difference in the amount absorbed.
Why this is the case, I am not completely sure.
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time to take my daily anavar with some espressos
