Most any drug can be delivered via mucus membranes, which is what vaping does. The nicotine is primarily absorbed through the mucus membranes in the mouth, not the lungs.
Caffeine is roughly equal to nicotine in it's risks. so you can see, 20% is a LOT. 24mg nicotine juice is 0.24% nicotine.
Things aren't absorbed well when you swallow them, which is why 56mg caffeine in a cup of coffee doesn't hit very hard. Absorbtion is bad, and the liver filters a lot out before it hits the bloodstream. I'd call 20% nicotine for mucus membrane absorption dangerous. 0.24%, OTOH, seems pretty safe.
I see a lot of cross over here. MG? ML? Gram? Not the same guys. MilliLiter= 1/1000th of a liter. There are 200 tsp in 1 liter. (1tsp = 5ml). Now a "cup" of coffee is aprox 6oz. (187.5 ml) With me so far? 1ml of water weighs 1 gram. (1000gram per kilogram or 5grams of water per tsp) *water is the universal conversion* Now.. that said.. 1mg = 1/1000th of a gram. OR if you convert to liquid 1/1000th of 1 ml. So as stated earlier.. 54MG of caffeine in 187.5 ml of coffee. (this is aprox since the calculations are based on water) means your coffee is actually 0.03% caffeine.
Now if you are trying to stay awake, and drink 4 cups of coffee per hour, for 2 hours. You figure how many ml of ejuice you vape per hour. Then make that 0.12% caffeine. or roughly 12mg per ml. So in 1L VG+flav+nicotine+pg you would want 1200mg or 1.2 grams of caffeine.
Now, the problem is this.. not 100% of what you inhale in vape actually gets into your lungs and not nearly 100% of what does get into your lungs stays there. So if we say... 10% stays in your lungs and 90% is exhaled. (you will have to look up the ACTUAL amounts.. im just using this for the math) you would need to multiply your 1.2gr/L by 10.. 12gr per liter. Now I use a dripper, and drip 10 drops every 30-60 minutes. So to get in my 4 cups of coffee I MUST vape 1ml (20 drops) per hour. Now if i only vape 10 drops per hour.. I have to double the caffeine again.. 2.4grams per 1000ml. Now 1000ml = 20 50ml bottles. Of which i use 2 to 3 per week.
Now according to
http://www.caffeineinformer.com/death-by-caffeine
LETHAL DOSAGE
After 92.1 cups of
Brewed Coffee, you'd be pushing up daisies. (based on 220lb man)
and that is 4968mg caffeine or almost 5grams per day. In other words.. you would have to vape over 2l or 40x 50ml bottles of juice in ONE day to come close to that amount if you used 2.4g per 1000ml. Needless to say, even if you put 10 times that amount in.. or 24g per 1000ml.. that is still vaping 4x50ml bottles in a day. You MIGHT do that if you used a theatrical fog machine and locked yourself in a closet.
Now, Im not recommending chain vaping e-juice with caffeine, but as a quick pick me up or to puff on in a tank while driving, or to stay awake an extra couple hours.. I doubt vaping a couple ml per day would kill ya.
IMPORTANT: All this is just converting ml to mg to gram to liters. To show you not to panic when talking about mg vs ml. If you add caffeine to your e-juice.. get your own calculation from that website i posted per your body weight, and start low and adjust your way up until you get the desired "awakeness" in a 1 hour period, per volume (mls) of ejuice. If you vape 1/2ml per hour adjust accordingly, if you vape 1ml per hour.. again adjust accordingly.
As you can see.. 2.4g or even 24g in 1000ml is FAR from a paste.
I'll probably start mixing mine at 1/8th gram per 50ml of (100ml vg+pg+flav+nicotine) and adjust from there. That way, I can double the caffeine simply by adding more.. or lessen it, by adding more of the ejuice component.
In other words.. if i vape for 15 minutes and start feeling my hair grow.. its time to switch to the 0 caffeine juice and cut my caffeine mix down more.
At any rate, start low according to what is comfortable for you and go from there, and use small dosages to regulate how much you intake. You want to stay awake.. but you don't want to feel your hair growing either.
And of course.. the only SURE way to know the difference between ingesting caffeine or inhaling it, just like nicotine from cigarettes, is with a blood content test.
By the way.. look into any known problems with inhaling caffeine vs ingesting it. I really don't know of any, since it is getting into your blood stream one way or another.. but i sure as hell wouldn't do lines of it like snorting pills or whatever.
See also:
http://www.huffingtonpost.com/entry/eagle-energy-vapor-caffeine_us_55c8c514e4b0f1cbf1e5a202
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