system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do such small doses of things like cocaine and heroin kill you? How do these small powders have such a big effect on your body?
gpt
It just doesn't always take a lot of something to have an effect in your body. Cocaine and heroin have different effects on the body, but in general, they target receptors in your brain that then set off cascading reactions all over your body.

Lots of medications have an effect at a much lower dose than the same weight cocaine and heroin. For example, a standard dose of the benzodiazapine clonazapam is 0.25mg. It's just formed into larger pills to make it easier to use.

The thing is, unadulterated cocaine and heroin *aren't* super deadly in small amounts...provided you are more or less healthy and not using other substances. It's when you start mixing substances (like, cocaine and alcohol is bad news for your liver and also increases the risk of heart attack) or using while you have a health condition (it should be fairly obvious why using something like cocaine when you have a heart condition is dangerous). Body weight, how frequently you use, how you use (like snorting versus injecting)...there are lots of different variables.

When you get into the truly hard-hitters like fentanyl, carfentanil, and other analogues, that's when things get beyond potent.