Is cocaine similar to alcohol, like, it takes more the heavier I am?

Does a 400lb man need to do more cocaine than say, a 195lb man? Granted, nobody should be doing cocaine and this thread does not advocate drug use, I’m curious to see if cocaine is similar to alcohol when it comes to working on an individual.

Not to hijack too much, but can I add a more general general question:

What kinds of substances are dosed linearly by body weight, and what kinds are not?

Great question. Thanks, because now we can get a possible list in one thread. Thanks, groman

Well, I’m no expert, but since cocaine’s effect does not rely on circulating in the bloodstream, I’d say “no.” Drugs that are snorted or smoked will hit the brain and do their thing before getting diffused.

Injecting heroin, swallowing pills – I’d think that these will be size-dependent.

Well, cocaine will keep doing it’s thing until fully metabolized. I don’t have a cite but I remember reading that only 1% of cocaine leaves the body unchanged. Since it is mostly metabolized in the liver, I would imagine it actively circulates in the bloodstream, with a small concentration crossing the blood-brain barrier and binding to receptors. I am also not an expert, but my guess would be is that after initial blood concentration peak the blood concentration will be dropping with a relatively stable half-life. Your blood concentration will obviously depend on dose vs. amount of blood, so my WAG is cocaine dosage is at least somewhat sensitive to body mass (+ liver health and enzyme competition).

What? Unless you’re injecting it intrathecally, every drug has to travel through the bloodstream before it gets to the brain and exerts its effects, right?

I think you’re right, chorpler.

And by what mechanism do they “hit the brain”?

I’d say yes, all other things being equal. The key is metabolism, as already pointed out, so you could easily have a wee man with elevated levels of a certain metabolism enzyme that would need more cocaine than a big man with lower levels. Similarly, a wee crackhead veteran would obviously have more tolerance than a big bloke who had never taken the drug. But if you have broadly similar metabolic profiles then the bigger guy will need a greater dose.

Any drug that needs to be dosed according to bodyweight would be described as having a narrow therapeutic window. The FDA won’t stand for this in general, as it is just introduces additional variables, additional monitoring that is going to reduce the safety of the drug - doctors making judgment calls on whether a big patient needs a greater dose than smaller people for example. There are exceptions though where the benefits outweigh the risks, the wiki on therapeutic index gives a few (lithium carbonate, vancomycin etc)

Yes, but lots of other factors are at play that determine the toxicity of cocaine. A full discussion can be found here: http://www.emedicine.com/emerg/topic102.htm

Amount of cocaine, route of administration, presence of aldulterants, coingestants including nicotine, alcohol and other drugs, previous use, metabolic ability to break down acetylcholine, etc. play a big role – so big that although most folks would be toxic at blood concentrations of 1 mg/L, quantitative blood levels are rarely useful since some folks would be toxic at 0.1 mg/L and some at 21 mg/L.

Thank you, Dr_Paprika