Hematocrit-Independent Quantitation of Stimulants in Dried Blood Spots: Pipet versus Microfluidic-Based Volumetric Sampling Coupled with Automated Flow-Through Desorption and Online Solid Phase Extraction-LC-MS/MS Bioanalysis.

A workflow overcoming microsample collection issues and hematocrit (HCT)-related bias would facilitate more widespread use of dried blood spots (DBS). This report describes comparative results between the use of a pipet and a microfluidic-based sampling device for the creation of volumetric DBS. Both approaches were successfully coupled to HCT-independent, fully automated sample preparation and online liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis allowing detection of five stimulants in finger prick blood. Reproducible, selective, accurate, and precise responses meeting generally accepted regulated bioanalysis guidelines were observed over the range of 5-1000 ng/mL whole blood. The applied heated flow-through solvent desorption of the entire spot and online solid phase extraction (SPE) procedure were unaffected by the blood's HCT value within the tested range of 28.0-61.5% HCT. Enhanced stability for mephedrone on DBS compared to liquid whole blood was observed. Finger prick blood samples were collected using both volumetric sampling approaches over a time course of 25 h after intake of a single oral dose of phentermine. A pharmacokinetic curve for the incurred phentermine was successfully produced using the described validated method. These results suggest that either volumetric sample collection method may be amenable to field-use followed by fully automated, HCT-independent DBS-SPE-LC-MS/MS bioanalysis for the quantitation of these representative controlled substances. Analytical data from DBS prepared with a pipet and microfluidic-based sampling devices were comparable, but the latter is easier to operate, making this approach more suitable for sample collection by unskilled persons.

Isolation of urinary p-hydroxylated metabolites of mephentermine and phentermine in male Wistar rats.

1. p-Hydroxymephentermine (p-hydroxy-MP) and p-hydroxyphentermine (p-hydroxy-Ph) were isolated as hydrochlorides from urine of male Wistar rats repeatedly dosed with mephentermine (MP). In addition, p-hydroxy-Ph was isolated as the hydrochloride from urine of the rats dosed with phentermine (Ph). 2. These results substantiate previous indications that p-hydroxylation of MP and Ph was a primary metabolic reaction in the rat.

Simple techniques to detect and identify phentermine adulteration.

Phentermine capsules labelled Ionamin were suspected of being counterfeit. Examination of the contents revealed no phentermine, but caffeine and phenylpropanolamine. The usual microcrystalline and spectrodensitometry was used to confirm results of spectrophotometric identity tests.