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reading toxicity mg per kg help

reading toxicology

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#1 normalizing

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Posted 21 December 2016 - 04:10 AM


didnt know where else to put this its not really related to other forums but it seems to fit here.

 

so to begin, im confused about all those studies that asses max toxicity levels in rats and other animals. it always says mg per kg and i cannot possible figure out how to calculate this to how much exactly mgs are used in the study. it has been confusing me for a long time too and i just have to ask and if not the proper place to do so i apologize.

 

here is an example of my confusion; https://www.ncbi.nlm...pubmed/11434987

 

"Because of pathological changes in male liver and hematological changes in females, the no-observed-adverse-effect level (NOAEL) was concluded to be 0.19% in the diet (120 mg/kg body weight/day for male rats and 130 mg/kg body weight/day for female rats)"

 

so what does 120mg/kg body means?? and what is the no observed adverse effect level mean? so it doesnt cause adverse effects, YET, it just mentions it DOES cause them! very confused!

 

here is how it ends; As a decrease in MCV, an increase in the A/G, elevation of alkaline phosphatase and increase in adrenal weight were observed in all treated males, a no-observed-effect level (NOEL) could not be determined in this examination.

 

ok, so they say adverse effects could be determined at the end, but they just did in the study and did find liver changes! so i dont get it.

 

anyway, main problem is, what program to use to calculate this 120mg/kg thing, PLEASE HELP!!!



#2 Dan Wich

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Posted 23 December 2016 - 04:44 AM

You may not always be able to calculate the total amount given to the animals without access to the full text of the studies. That's because the mg/kg values are used to scale the dosage to the bodyweight of the animals used. That way larger animals get more of the substance, and you can potentially generalize to humans.

I've attached two figures from that study to let you figure out how much was used in each group:
Attached File  nakamura-figure2.png   113.33KB   0 downloads

Attached File  nakamura-table1.png   175.29KB   0 downloads

I didn't read carefully enough to see how they adjusted the dosages, but you can probably assume that a male in group 1 got around 12-35mg per day, for example, since their weights were around 100-300g. So for a 70kg human male (assuming we can generalize to humans), that's around an 8g per day equivalent. 

 

When they say they couldn't determine a No-Observed-Effect-Level, I think they mean they can't determine a dosage that won't lead to observable effects because all the dosages they tried had effects (not necessarily *adverse* effects).


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#3 Oakman

  • Location:CO

Posted 23 December 2016 - 04:34 PM

I had similar difficulties when trying to concoct the 'best' dosages for some supplements based on animal studies, so I went looking....

 

Below is some of the reading I looked through. In summary (my opinion), a human equivalent dose, no matter what type of level you are looking to determine, is a best guess,

divided by a safety factor of 10-100 for use in humans.  Obviously, that's a gross oversimplification of the calculations involved, but that seems to be the case with these types of numbers.

 

www.fda.gov/downloads/drugs/guidances/ucm078932.pdf

https://www.ncbi.nlm.nih.gov › NCBI › Literature › PubMed Central (PMC)

http://www.ema.europ...WC500010862.pdf

 

Hope this helps a bit.

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#4 YOLF

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Posted 26 December 2016 - 03:38 PM

Did anyone mention allometry? You could use that to get the numbers you're looking for.






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