Wondering About... The Mechanics? Of I.V. injections

[snazzy_sn]

I'm not to learned in biology, or science, or medicine but...
I always here people talking about how when you inject, it goes straight to your heart, or straight to your brain.

Neither of these make sense to me as it seems to me it would take a lot more time for the blood in your foot to reach your heart than the time it takes to begin feeling the effects.

I came up with some theory based on ignorant thought, that once the drug reaches the blood stream it somehow hits the CNS and spreads like that throughout the body.

I'm trying to figure out the best place to inject for scientific reasons other than "it hits your brain faster" or "it hits your heart faster".
But even if I weren't a junkie I'd be curious.

What exactly happens after the drug hits your bloodstream? Or your heart for that matter? What happens in the heart? The brain I understand, but from what I've gathered most of the action from like methamphetamine occurs in the CNS so it wouldn't really matter that much...

I dunno. Ideas?

 

[nAON]

In general if you're injecting into a vein, it's going to go through to your heart, then to your lungs, and then from there it'll to your brain and around your body. It's only going to take like 10 seconds for all that to occur.

 

[nsauce]

Also, yes it will take longer for blood in your leg to reach vital organs than blood in your arm or hand.

 

[effie]

What happens to the drug is as nAON said - veins -> heart -> lungs -> heart -> rest of body (inc brain, also liver where the drug may be metabolised and kidneys where it may be excreted).

The effect it has depends on the drug and where it targets. Psychoactive drugs affect receptors within the brain - for example opioid receptors, serotonin receptors, dopamine receptors or GABA receptors. A psychostimulant such as methamphetamine affects the heart via the central nervous system - it is the effect it has in the brain that causes your heart rate to increase and blood vessels to constrict. Other drugs work by affecting receptors within the end-organ (for example, beta-blockers such as propranolol affect the beta receptors in the heart, blocking the action of one branch of the peripheral nervous system and slowing the heart rate down, amongst other things.) Other drugs work by influencing local cellular signalling, or by killing bacteria, or affecting hormonal production, or by other mechanisms..

If you are interested in how recreational drugs affect the brain, do some reading around on BL - if you want to know a lot, invest in a good psychopharmacology text book or read Advanced Drug Discussion

It takes a varying amount of time for blood to travel around your body (depending on the route it takes and other factors) but on average a blood cell travels all the way round and back in about a minute. The further away from your heart/brain you inject, the longer it will take for it to hit the receptors in your brain, but this really isn't going to make a significant difference. Most of the time is spent by the blood cells making their way through the the tiny capillaries in your tissues - once the blood reaches a vein, it shoots to your heart and therefore brain pretty fast wherever it is.