Hey guys,
I was hoping one of you chemistry whizzes might be able to help me.
I, for all intents and purposes, flunked high school chemistry. Now, I'm trying to analyze a medical journal article, but to do so, I need to figure out how much of a specific substance is present in a given dosage, and every time I do the math, the result I obtain doesn't seem feasible. Here's what I'm trying figure out:
A subject is given a dose of 100 μL of 10 μM via subcutaneous injection of a substance with molar mass 302.236. I'd like to know how much of the substance is present in each dose.
The article mentions that the substance is (presumably dissolved) in 10% dimethyl sulfoxide in phosphate-buffered saline. I didn't feel that part was relevant with regard to calculating the amount in each dose, but maybe this is the source of my error?
Anyway, when I do the math, it yields 0.000000302236 g, or 3.02236 x 10-7 g.
Now, granted, the subjects in this experiment were lab mice (which I estimate at 24 g to 25 g at the time of administration), but 0.000302236 mg per dose (one daily) seems absurdly low to me when you consider that the suggested oral dose in humans is on the order of a gram and up.
Assuming my 24 g estimate of mouse weight, 0.000302236 mg / 0.024 kg bodyweight yields 0.012593167 mg/kg, while the suggested dose for humans is in the range of 12.5 to 25 mg/kg. No conversion from mouse to human or vice-versa that I can find would justify these results.
I realize that subcutaneous injection probably results in much greater bioavailability, but I still can't imagine that explaining such an enormous disparity in relative dose.
I'm assuming that my calculation must be woefully incorrect. Can anyone confirm this result? I'm happy to take you through my steps so you can all have a laugh.
Thanks,
Chris