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 CrimpJiggler
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 How are drugs excreted via the urinary system? 
#15113332 - 09/21/11 06:29 PM (12 years, 6 months ago) |
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I'm trying to get my head around how drugs are passed through the body and ultimately excreted (unmetabolised or as metabolites). I know some of you here are med students or just very knowledgeable this kinda stuff, can you help me fill in some of the gaps in my knowledge. Alright lets say I ingest a drug intravenously so it is now dissolved in my blood plasma. Lets say I injected it into a vein in my arm. Veins carry blood back to the heart so the drug will get carried there. If I'm not mistaken there are only 2 veins that carry blood into the heart besides the pulmonary veins so the drug will be carried into the hearts right atrium via the superior or inferior (dunno which one) vena cava. The drug then gets carried into the right atrium. From there it gets fed into the pulmonary artery and carried to the lungs so if I'm not mistaken, any gaseous metabolites of the drug will be excreted via the lungs. So the drug then gets pumped back into the heart via the pulmonary veins and enters the left artium. From there it goes into the left ventricle and this is where theres a major gap in my knowledge.
What happens when it reaches the left ventricle? Does the blood just get pumped out of all the different arteries of the aorta so that only a fraction of the blood will get pumped out the abdomenal aorta towards the kidneys? In other words only some of the drug will go towards the kidneys while the rest will get pumped out the other parts of the aorta so some of it goes towards the brain, some to the arms, some to the legs etc.?
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ChuangTzu
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Re: How are drugs excreted via the urinary system? [Re: CrimpJiggler]
#15113946 - 09/21/11 08:24 PM (12 years, 6 months ago) |
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Quote:
CrimpJiggler said:
In other words only some of the drug will go towards the kidneys while the rest will get pumped out the other parts of the aorta so some of it goes towards the brain, some to the arms, some to the legs etc.?
That's right, but the blood continually circulates from the heart, out to the body, back again, and then out again until eventually, everything passes through the kidneys.
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Kizzle
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Re: How are drugs excreted via the urinary system? [Re: CrimpJiggler]
#15114478 - 09/21/11 10:09 PM (12 years, 6 months ago) |
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I think that's how it works, that all the blood is through the lungs and back to the heart and from there to everywhere else. So not all of the blood is going through the kidneys each cycle. Then anything the kidneys aren't able to reabsorb into the blood stream go to the bladder.
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imachavel
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Re: How are drugs excreted via the urinary system? [Re: Kizzle]
#15115035 - 09/22/11 12:04 AM (12 years, 6 months ago) |
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maybe, but I thought drugs weren't detected in your urine. I thought your blood ph, or some other chemical your body excretes when drugs enter your system is what is detected in your urine
how can they detect thc in your urine if you smoked the joint 25 days ago? I thought the thc changes your metabolism slightly or something along those lines, which excretes a ph or something that turns a color in your urine
am I wrong??
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Kizzle
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Re: How are drugs excreted via the urinary system? [Re: imachavel]
#15115155 - 09/22/11 12:38 AM (12 years, 6 months ago) |
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Quote:
imachavel said:
maybe, but I thought drugs weren't detected in your urine. I thought your blood ph, or some other chemical your body excretes when drugs enter your system is what is detected in your urine
how can they detect thc in your urine if you smoked the joint 25 days ago? I thought the thc changes your metabolism slightly or something along those lines, which excretes a ph or something that turns a color in your urine
am I wrong??
What they look for in your urine depends on the drug. Either the original drug or a metabolized version of the original drug or both.
What I've heard is that THC tends to become concentrated in the fats in your body. It's more soluble in oils than water so it takes longer for your body to get rid of it all. So even after most of it is gone there are still detectable traces of it for some time.
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CrimpJiggler
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Re: How are drugs excreted via the urinary system? [Re: Kizzle]
#15117487 - 09/22/11 02:17 PM (12 years, 6 months ago) |
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double post
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…...,~__________________, ,.
….../ `—___________—-___]Give a man a gun
…../_==o;;;;;;;;_______.:/he can rob a bank.
…..), —.(_(__) /
….// (..)),````
…//__/Give a man a bank,he can rob the world!
.//__/
Edited by CrimpJiggler (09/22/11 02:43 PM)
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CrimpJiggler
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Re: How are drugs excreted via the urinary system? [Re: imachavel]
#15117582 - 09/22/11 02:42 PM (12 years, 6 months ago) |
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Quote:
ChuangTzu said:
That's right, but the blood continually circulates from the heart, out to the body, back again, and then out again until eventually, everything passes through the kidneys.
Ah yeah thats what I was wondering, thanks.
Quote:
Kizzle said:
I think that's how it works, that all the blood is through the lungs and back to the heart and from there to everywhere else. So not all of the blood is going through the kidneys each cycle. Then anything the kidneys aren't able to reabsorb into the blood stream go to the bladder.
Yeah take a look at this diagram:
as you can see the only ways into the heart are the pulmonary veins and the superior and inferior vena cava. All blood that enters the heart through the vena cava will pass through the lungs before being pumped back out the aorta. So yeah the blood will go through the lungs each cycle but not through the kidneys each cycle.
Quote:
imachavel said:
maybe, but I thought drugs weren't detected in your urine. I thought your blood ph, or some other chemical your body excretes when drugs enter your system is what is detected in your urine
how can they detect thc in your urine if you smoked the joint 25 days ago? I thought the thc changes your metabolism slightly or something along those lines, which excretes a ph or something that turns a color in your urine
am I wrong??
When you inhale THC it enters your blood stream and will be carried around your body. Throughout the body (but mainly at the liver), the drug gets metabolised into simpler molecules that can be excreted easier. The blood is constantly carrying the drug and its metabolites through the kidneys and some of it gets excreted. The metabolites are easier to excrete (thats pretty much the reason why the body metabolises drugs instead of just excreting them as they are) so there will be a lot more metabolites in your piss but unmetabolised THC does get excreted so you will be able to detect it in your piss if the test is sensitive enough. In your scenario where you smoked a joint 25 days ago then I suspect there will be little or no THC or metabolites in your piss. The only reason there may be any of it at all is because sometimes drugs get deposited in fatty tissue and can remain there for months. Piss tests are only effective for finding out if someone has taken a drug "recently". For more long term testing a hair follicle test is more effective. Drugs get deposited in the hair as it grows so a long haired hippy won't fare out well in a hair follicle test lol. I get my hair cut twice a year so if the barber was to run a drug test on a strand of my hair he would find out that I like my psychoactive substances. A breathaliser test on the other hand can only tell you about very recent drug use, similar to piss tests. I noticed they sell home drug test kits at my local pharmacy. They're expensive (€30) but I'm gonna one some day soon to see how well they work.
EDIT: ^^ I'm not entirely sure about everything I said there. I've heard people claim that some drugs like THC can only be detected days after it was ingested while others like heroin can be detected weeks after. I don't know if they are referring to a urine test, blood test or what but I don't understand why some drugs can be detected weeks later while others only days after. With a hair follicle test, it should be a matter of how long the hair is, not the drug in question unless of course some drug in the hair get gradually oxidised by the air or something. As for blood tests and urine tests, why can heroin be detected weeks after it was ingested? Like I said some drugs get deposited in fatty tissue and get released back into the blood stream gradually which can take months. Is that why these drugs can be detected weeks after they were ingested? I'm gonna start a new thread on drug testing.
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…...,~__________________, ,.
….../ `—___________—-___]Give a man a gun
…../_==o;;;;;;;;_______.:/he can rob a bank.
…..), —.(_(__) /
….// (..)),````
…//__/Give a man a bank,he can rob the world!
.//__/
Edited by CrimpJiggler (09/22/11 02:52 PM)
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5HTSynaptrip
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Re: How are drugs excreted via the urinary system? [Re: CrimpJiggler]
#15118084 - 09/22/11 04:23 PM (12 years, 6 months ago) |
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Hepatic portal veins and arteries carry a lot of blood to that enzymatic workhorse. So if you take a drug via any ROA it ultimately passes through the liver, and oral administration can obviously cause first-pass metabolism due to enzymes in the GI tract along with direct entry into the hepatic portal system. The type of drug, and consequently how the body metabolizes it, plays a role in renal excretion. It's hard to explain in a post without typing a wall of text but this site offers a good explanation: http://sonet.nottingham.ac.uk/rlos/bioproc/kidneydrug/3.html
Amphetamines for example can be excreted faster depending on urinary pH. There are different systems of excretion, filtration, and resorption. The process of elimination varies between a drug and the metabolites created from it.
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