There is a good Q/A on this from Erowid (http://www.erowid.org/ask/ask.php?ID=2871):
I believe the half life of MDMA is 9 hours (+/- 2.25 hours). If you redo your otherwise correct calculation, you get less than 1% remaining at 72 hours (rather than 48).
However, this is only one step of the calculation as far as how long MDMA is detectable in urine. MDMA is metabolized into a variety of other molecules including HMMA, MDA, and HMA. Respectively these have half-lives of approximately 11, 25, and 37 hours. MDA triggers the standard Amphetamine urine test, while MDMA itself will trigger a Methamphetamine urine test. We don't have any information about whether HMMA or HMA metabolites will trigger the amphetamine/methamphetamine test in a urinalysis and whether the quantities present from MDMA metabolism are sufficient for such a trigger.
As you also state, there are many factors which go into determining how long a substances is detectable in urine. The specific metabolism of the person being tested, the amount and frequency used, the method of administration, fluid intake, amount of exercise, etc.
Traditional urine tests are somewhat unreliable at detecting MDMA use with an Amphetamine test, but there are several new test designs out which are supposed to be quite a bit more reliable. At this point we believe that MDMA is detectable for approximately the same duration as Amphetamine/Methamphetamine (3 days average, up to 5 days with heavy frequent use), but we haven't seen conclusive data on this.
Assuming a dose of 150 mg MDMA, according to this only .0015g would be left in the system. However, urine tests test for metabolites as well as the original drug, so it is important to note
HMMA, MDA, and HMA. Respectively these have half-lives of approximately 11, 25, and 37 hours.
Math confuses me, but the half life formula is pretty simple.
- N0 is the initial quantity of the thing that will decay (this quantity may be measured in grams, moles, number of atoms, etc.),
- Nt is the quantity that still remains and has not yet decayed after a time t,
- t1 / 2 is the half-life of the decaying quantity
So, e.g. for MDMA's major metabolite, MDA, you would have to know how much MDMA is metabolized to MDA (which I don't), which I will assume is 10% for the sake of facility:
Originally 150 mg MDMA x .01 = 15 mg MDA
Let us say it has been 24 hours since ingestion
Nt= 15mg x (1/2)^(24hrs/37hrs)
Nt= 9.56mg (63%%)
For comparison, after 5 days (120 hours):
Nt= 15mg x (1/2)^(120hrs/37hrs)
Nt= 1.58mg (10%)
After 10 days (240 hours):
Nt= 15mg x (1/2)^(240hrs/37hrs)
Nt= .167mg (1%)
moda00 Re: how long does ecstasy stay in your system
I don't mean to be dense.. but could someone explain exactly how this works and why? For example, in a urine test, what chemical substances or metabolites are tested for in order to come up for amphetamines? Along those lines, if they weren't specifically trying to distinguish MDxx use, any MDxx would show some characteristic chemical or metabolite that an amphetamine such as say amphetamine sulfate like in Europe, or ADHD meds in the US like Dexedrine (d-amps) would also have? What is this chemical marker that they share, specifically tested for and identifiable in urine?
And if they were to then do a specific test for MDxx, what would be the different way of telling this apart, and would say someone who ingested pure MDxx (not cut with amps or any other drugs) then test positive for both MDxx AND amphetamines? Also, I thought they could distinguish between amps and methamp- am I totally off base on that? Because wouldn't methylenedioxymethamphetamine (MDMA) be more likely to show up as methamphetamine than amphetamine-- obviously it is not classified as either.. but I'm guessing it's something to do with that structure/skeleton being a part of the overall compound- is any MDxx excreted intact in urine, or is it broken down into other compounds?
Again, I don't know much about this, and forgive me if this is off topic, but I am just wondering so that I can best understand the question being posed and how to answer it. Thanks.
Here is a good article about MDMA metabolites: http://www.drugs-forum.com/forum/sho...ma+metabolites
three of its main metabolites, 3,4-methylenedioxyamphetamine (MDA), 4-hydroxy-3-methoxyamphetamine (HMA), and 4-hydroxy-3-methoxymethamphetamine (HMMA)
Basically, because a lot of commonly abused drugs have specific metabolites, most urine tests test for their presence and the presence of the original drug. There is a cutoff concentration of I believe 1000 nanograms/l. If tests just tested for the chemical in question then no one would ever get caught. The longer the half lives of a drug's main metabolites, the longer the metabolites stay in the system. That is why some drugs can be detected only a few hours after, and some a few weeks.
From what I understand, most urine tests work like this:
The urine is separated into two portions. On the first portion, an immunoassay is done. Since biologically speaking, all drugs are foreign bodies, our bodies produce antibodies for them (and correspondingly their metabolites, I believe only if they are active?) the first time we ingest them. I believe the immunoassay introduces antibodies for e.g. opioids/ metabolites, amphetamines/metabolites, etc. to the urine. Concentrations can then be detected using a variety of techniques. If the test is positive, GC/MS (Gas Chromatography/Mass Spectrum, a more advanced, accurate, and expensive technique for determining the presence and structure of molecules) is performed on the other portion of urine to confirm the results of the immunoassay.
I believe that the fact that e.g. MDMA and amphetamine are similar in structure means that so are their metabolites, so the antibodies introduced in the immunoassay react with the metabolites of both drugs or because their structure is similar, a lot of drugs share common metabolites.
As far as meth vs amphetamine, methamphetamine's main metabolite is amphetamine, and therefore once it is metabolized to amphetamine it will break down the same way that amphetamine does and they will both test positive.
Structure is important in metabolism. Similar molecules will be metabolized similarly. I believe that MDxx chemicals, and for that matter many structurally-related opioids, etc. have similar if not some of the exact same metabolites, hence why urine tests usually test for classes of drugs rather than MDMA vs MDEA.
The most common test, the 5-panel or something like that tests for major classes. I imagine there are specific tests that can be done to differentiate among substances in a class if the tester is so inclined.
Anyway, I would say a general guideline for MDMA detection is about 3 days, give or take. MDMA is water soluble so exercise, overhydration, etc. can speed up excretion. There are a ton of factors which affect metabolism so no one can really say exactly how long a drug will every stay in the system.