A hair methamphetamine concentration is not a simple dose meter. In a controlled human experiment, higher administered doses generally produced higher hair concentrations within the same person, but concentrations differed substantially between people receiving the same regimen. Those findings answer different questions and should be reported together.
What was controlled in this experiment?
Polettini and colleagues’ 2012 paper studied seven volunteers with stimulant-use histories in an inpatient unit. After a washout period, participants received four oral 10 mg doses of sustained-release S-(+)-methamphetamine hydrochloride within one week. Four participants later completed a higher regimen of four 20 mg doses after a three-week interval.
The administered totals were therefore 40 mg and 80 mg of the specified hydrochloride preparation, spread across dosing occasions. They were not single 40 mg or 80 mg doses. Timing sometimes departed from consecutive-day administration because of clinical or scheduling considerations.
Controlled access reduced the possibility of additional drug use and environmental drug-smoke exposure during the experiment. It did not eliminate drug reaching hair through participants’ own sweat or sebum.
How was hair collected and measured?
Investigators repeatedly shaved newly available scalp hair, usually in approximately weekly collections, with actual intervals ranging from five to twelve days. The main analysis used posterior-vertex hair. Methamphetamine and amphetamine were quantified by liquid chromatography–tandem mass spectrometry after washing; the lower quantification limit was 0.005 ng/mg for each analyte.
This collection method followed successive newly emerging hair samples. It differs from cutting one long strand into segments after several months. The resulting timeline should not be transferred unchanged to routine segmental testing.
How much did concentrations vary?
Peak methamphetamine concentrations ranged from 0.6–3.5 ng/mg after the lower regimen and 1.2–5.3 ng/mg after the higher regimen. The corresponding amphetamine ranges were 0.1–0.3 and 0.2–0.5 ng/mg. These ranges overlap across dose conditions.
Within individuals, the higher regimen generally produced greater incorporation. Across individuals, however, someone receiving the lower regimen could have a higher hair result than someone receiving the higher regimen. A within-person dose relationship does not establish a universal between-person conversion equation.
Why did pigmentation matter?
The study measured total hair melanin and found positive associations with methamphetamine and amphetamine incorporation. Some of the strongest reported relationships used body-weight adjustment and logarithmic transformation. They should not be described as a simple unadjusted correlation applying equally to every sample.
The finding supplies a biological reason for caution when ranking people by hair concentration. It does not establish an individually validated “melanin correction” that allows an analyst to calculate an unknown consumed dose. The small cohort and only four higher-regimen completers limit that possibility.
Can the peak date identify the exact day of use?
Drugs were first detected in the first scheduled postdose hair samples, collected six to eight days after the initial dose. That is the earliest sampled detection, not proof that hair was negative at every earlier moment. Methamphetamine peaks occurred in the first or second weekly sample, even among participants with similar dosing schedules.
Growth variability, specimen location, washing and collection intervals all affect interpretation. The study also found that washing removed different amounts over time. A wash result therefore needs the actual collection and preparation protocol rather than a generic label of “decontaminated.”
The defensible historical conclusion is that controlled dosing supports a dose-related incorporation process, while substantial biological and sampling variation prevents straightforward dose reconstruction from another person’s hair concentration. A hair result also does not supply a contemporaneous blood concentration or establish functional impairment on a particular date.
Source
Polettini A, Cone EJ, Gorelick DA, Huestis MA. Incorporation of methamphetamine and amphetamine in human hair following controlled oral methamphetamine administration. Analytica Chimica Acta. 2012;726:35–43. doi:10.1016/j.aca.2012.01.042.
Leave a Reply