Plasma amphetamine(s) analysis should be considered when the patient cannot provide a urine drug test, and may be subject to Pathologist approval.
Methamphetamine > 100 ug/L can be associated with significant symptoms such as rapid or confused speech, dilated pupils, agitation, paranoia and rapid pulse.
MDMA > 100 ug/L associated with recent recreational dose of MDMA.
Uncertainty of Measurement
Amphetamine: 16%Methamphetamine: 16%
LCMS
In the Auckland Region, wastewater analysis indicates more methamphetamine is consumed than MDMA [4]. The plasma amphetamines analysis uses mass spectrometry to detect three drugs in plasma: Amphetamine, Methamphetamine and MDMA. This plasma amphetamine assay is not intended to detect novel psychoactive substances (e.g. cathinone) or other amphetamines such as MDEA, MDA, PMA, ephedrine and phentermine.
This test differs from the urine amphetamine test (see amphetamine urine) offered as part of a urine drug screen, initially by immunoassay and confirmed, if necessary, by mass spectrometry. The urine immunoassay detects more amphetamine-type substances but does not differentiate between them.
Plasma amphetamine(s) analysis should be considered when the patient cannot provide a urine drug test, and may be subject to Pathologist approval.
- The detection windows for urine methamphetamine and amphetamine are usually between 1-5 days. In contrast the detection window in plasma is shorter (see below).
- Peak amphetamine concentrations typically rise within minutes by the intravenous route, in about 30 minutes by the intramuscular, topical or nasal route, and within 2-3 hours after oral ingestion.
- Low concentrations of plasma amphetamine(s) may reflect recent ingestion, poor absorption, or delayed sample testing. In these instances, correlation with history is important and if necessary, consider repeat urine or plasma amphetamine testing.
Methamphetamine:
Methamphetamine is metabolized to amphetamine in the liver (by aromatic hydroxylation, N-demethylation and deamination); therefore, amphetamine is usually detected in the presence of methamphetamine but maybe 10 times lower in concentration. This mass spectrometry method cannot distinguish between L and D forms of methamphetamine.
-
D-methamphetamine (commonly found in illicit drug abuse):
- Half-life typically ranges from 6-15 hrs in plasma (compared to an average of 22-23 hours in urine) [1].
- Detection window vary with dose and route of ingestion and are usually between 24-48 hours [3].
- Time to positive result varies between 0.5-2h after 10-20mg oral ingestion (Positive > 2.5 ug/L) [2].
-
Plasma Concentrations:
- 50 - 2600 ug/L - reported in impaired drivers [1].
- > 100 ug/L - Rapid or confused speech, dilated pupils, agitation, paranoia and rapid pulse [3].
- > 300 ug/L - Violent behaviours associated with arrest [3]
- L-methamphetamine (this isomer has a weaker central stimulant action and may be found in some nasal decongestants or metabolites of selegiline):
- Half-life is typically around 13-15 hours in plasma (usually longer than D methamphetamine) [1].
Amphetamine:
May be used as a treatment for ADHD and narcolepsy
- Half-life is typically between 7-34 hours. 30-40% of amphetamine is excreted unmodified by the kidneys, with the clearance rate dependent on urine pH.
- In 48 adults with impaired driving amphetamine, concentrations ranged from 30 - 2300 ug/L.
- Time to positive plasma results varies between 1-24h (positive > 2.5 ug/L) [2].
Methylenedioxymethamphetamine (MDMA; Ecstasy):
- The half-life is between 5-9 hours [1]. Troublesome after-effects may occur for one to two days after ingestion (5 half-lives = 40 hours).
- Typical doses used for recreational purposes varies between 50 - 150 mg. Recreational use of MDMA typically produces blood levels of > 100 ug/L [5]
References:
- Disposition of toxic drugs and chemical in man 8 th Edition
- Huetis M et al., Methamphetamine Disposition in Oral Fluid, Plasma, and Urine. Ann N Y Acad Sci. 2007.
- Cruickshank et al., A review of the clinical pharmacology of methamphetamine. Addiction, 2009
- New Zealand Police. National Wastewater Testing Programme Quarter 4 2021. Retrieved 09 May 2021 from http://police.govt.nz/sites/default/files/publications/wastewater-results-quarter-4-2021.pdf
- Kalant H, The pharmacology and toxicology of ?ecstasy? (MDMA) and related drugs. CAMJ 2001;165(7):917-28
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427
Centrifuge and separate sample and transport at 4 o C.