What would happen if you took alcohol intravenously? — Balaram, Bhubaneswar, India
Marshall Brain Answers:
First let’s state up front that injecting alcohol is a bad idea for reasons we will discuss below. Do not inject alcohol. But it is an interesting thought experiment that helps to understand the effects of alcohol, so let’s jump in.
Most people get their alcohol by drinking it, say in the form of beer or wine or moonshine. Ethanol molecules are absorbed into the bloodstream through the lining of the small intestine in the same way that food molecules are absorbed.
The thing about drinking alcohol this way is that it takes time for the alcohol to get absorbed. The amount of time depends on things like what you are drinking, how quickly you drink it and how much food you have in your stomach. It might take 20 minutes for you to notice significant effects.
Meanwhile the liver is busy processing the alcohol to eliminate it from the bloodstream (you exhale some of the alcohol and urinate some of it, but the liver does 90% of the processing). That takes time too. According to the article, “As a rule of thumb, an average person can eliminate 0.5 oz (15 ml) of alcohol per hour.” So if you drink 1 ounce of 100 proof moonshine, you are drinking 0.5 ounces of alcohol. It is going to take time for that alcohol to enter the bloodstream, and an hour later it will be mostly gone.
This graph shows what happens when a 75 kg (165 pound) person drinks 5 ounces of 100 proof moonshine containing 60 grams [*] of ethanol. You can see that it takes more than an hour for it to all get absorbed and for the BAC (blood alcohol content) to peak. Then it takes 5 or 6 hours for the liver to eliminate all of that alcohol. You can also see that food in the stomach slows down the absorption rate and the height of the peak. This alcohol calculator shows approximately the same effect.
Now let’s say that instead of drinking the alcohol, you inject pure ethanol straight into a vein [**]. For example, say you inject 2.5 ounces of ethanol (the amount of alcohol in 5 ounces of 100 proof moonshine) right into the bloodstream. The big difference is the time. Instead of it taking an hour for the alcohol to absorb, the alcohol is all there instantly. That’s 60 grams of alcohol straight into a bloodstream containing approximately 5 liters (5,000 grams) of blood. There will be a moment or two where the blood alcohol concentration is 60 / 5,000 – a toxic, possibly fatal level – before that alcohol diffuses into the water and fat of the entire body and falls by a factor of 10 to 60 / 50,000 [***].
So to answer your question, there really isn’t any chemical difference between drinking and injecting alcohol. In both cases you have ethanol molecules flowing in the bloodstream. But there is a big time difference. And because of the time difference you would need to be extremely careful in the amount injected. A mistake could be fatal. It would be good to apply the “don’t try this at home” rule.
[*] – 5 ounces (150 ml) of 100 proof moonshine contains 75 ml of ethanol. That ethanol weighs 60 grams because the density ot ethanol is 0.79 g/ml.
[**] – Note that we are talking about injecting pure ethanol, NOT moonshine. As Brian points out in the comments, injecting moonshine or whiskey into the bloodstream would not be smart because of all the impurities.
[***] – If the person weighs 75 kilograms, why is 50,000 grams used here? Because a person is 60% water and some percent fat. Not all 75 kilograms of the body will absorb alcohol.