Are you wondering how long Vyvanse stays in your system?
The answer to this question is not as straight forward as you might think for two reasons:
The half-life of Vyvanse is about 1 hour. Therefore, after 4 hours the vast majority of ingested Vyvanse will have been eliminated (only 6.125% of the drug will remain in your system). Take a look at Fig 1 above. You'll notice that after 4 hours the concentration of Vyvanse (lisdexamfetamine) approaches zero.
But the active metabolite d-amphetamine has an elimination half-life of ~10 hours (9 - 11 hours). So after 40 hours, a little less than 93.875% of the d-amphetamine will be cleared from your system. Or put the other way: after 40 hours, all but 6.125% of the d-amphetamine will remain.
Despite the fact that it take a long time for the d-amphetamine released from Vyvanse to be eliminated systemically, the concentration and alerting effects of Vyvanse only last about 12 hours.
D-amphetamine sticks around for days but the cognitive effects (e.g., increased concentration) only last for a day at most. Why does d-amphetamine linger in your system even though you might not feel its effects?
The answer to this question is two-fold. First, over time d-amphetamine levels drop below the therapeutic window. Second, the sites in your brain where dopamine is stored becomes depleted. Dopamine is stored in vesicles inside brain cells (neurons). d-amphetamine triggers dopamine release from these vesicles.
To better explain what I mean about Vyvanse's elimination half-life vs d-amphetamine's half-life, see this table:
|Time after ingestion (hours)||Vyvanse (% remaining)||D-amphetamine (% remaining)|
There are many kinds of drug tests capable of detecting d-amphetamine, the metabolite of Vyvanse (lisdexamfetamine). Lisdexamfetamine is hydrolyzed in red blood cells, which releases the amino acid lysine and d-amphetamine.
The following drug tests can be used to detect d-amphetamine:
While urine tests are the most common method to detect Vyvanse, a hair test might be used in some situations because it offers a longer window of detection.
Amphetamines remain detectable in your urine for up to 3 days after ingesting Vyvanse. D-amphetamine may be eliminated by some people more quickly than others depending on their urinary pH.
The threshold level of d-amphetamine required to test positive on a typical urine test is 1000 ng/ml. Nevertheless, if the urine is analyzed using gas chromatography/mass spectrometry (GC/MS), the cutoff is reduced to just 500 ng/ml[^2]. Therefore GC/MS is a more sensitive laboratory method.
A technician may collect a hair sample to discover whether you've ingested amphetamines in the last month. Though d-amphetamine released by Vyvanse wouldn't be detectable on a hair test immediately it can show up in hair within a week or two.
Hair testing is less common than urinalysis. Nevertheless it might be preferred due to the broader window of detection. Hair follicles (at least 3 cm) are normally taken off a person's head and examined with gas chromatography/mass spectrometry (GC/MS) to determine previous amphetamine usage [^3].
Saliva testing involves HPLC (also known as high-performance liquid chromatography). An advantage of HPLC is that provides a quick turnaround of about 15 minutes.
However, d-amphetamine does not remain in saliva as long as it remains in urine. D-amphetamine can be detected in saliva for up to 2 days. Chronic Vyvanse use and alkaline blood pH prolongs this time.
Saliva testing will become more popular as the technology improves and costs decrease. When saliva testing becomes more widely available it will allow health professionals and law enforcement to rapidly detect amphetamine [^4].
It's unlikely that you’d be tested for Vyvanse or d-amphetamine with a blood test. Here's why:
For these reasons, the other drug testing methods (like urinalysis) are more common. Some health professionals may use a blood draw to detect dextroamphetamine if somebody is hospitalized and/or fails to cooperate having a law enforcement representative.
[^2]: Poklis A, Still J, Slattum PW, Edinboro LF, Saady JJ, Costantino A. Urinary excretion of d-amphetamine following oral doses in humans: implications for urine drug testing. J Anal Toxicol. 1998;22(6):481-6.
[^3]: Roberts JK, Cook SF, Stockmann C, Rollins DE, Wilkins DG, Sherwin CM. A Population Pharmacokinetic Analysis of Dextroamphetamine in the Plasma and Hair of Healthy Adults. Clin Drug Investig. 2015;35(10):633-43.
[^4]: Stegmann B, Dörfelt A, Haen E. Quantification of Methylphenidate, Dexamphetamine, and Atomoxetine in Human Serum and Oral Fluid by HPLC With Fluorescence Detection. Ther Drug Monit. 2016;38(1):98-107.