Pervasive Gabapentin Interference in the LC-MS/MS Analysis of Amphetamine.

Background: An LC-MS/MS urine confirmation assay was developed using a "dilute and shoot" sample preparation method that was subject to interference arising from gabapentin column overload in approximately 4% of patient samples, leading to interference in amphetamine analysis.

Methods: The initial analysis method used dilute and shoot sample preparation followed by LC-MS/MS analysis. The improved assay used solid-phase extraction sample preparation followed by LC-MS/MS analysis.

Comparison of Information-Dependent Acquisition on a Tandem Quadrupole TOF vs a Triple Quadrupole Linear Ion Trap Mass Spectrometer for Broad-Spectrum Drug Screening.

Background: Liquid chromatography high-resolution mass spectrometry (LC-HRMS) with untargeted data collection is especially attractive for general unknown drug screening owing to its ability to identify unexpected compounds. LC-HRMS offers several advantages over traditional selected reaction monitoring (SRM) techniques and could be an ideal screening platform as long as its analytical performance is comparable to that of SRM-based methods.

Methods: We developed a broad-spectrum drug screen on a high-resolution mass spectrometer [tandem quadrupole time-of-flight (QqTOF)] that collected data in an untargeted manner and compared its performance to a nominal mass instrument [triple quadrupole linear ion trap (QqLIT)] that collected data in a targeted manner.

Measuring the overall genetic component of nevirapine pharmacokinetics and the role of selected polymorphisms: towards addressing the missing heritability in pharmacogenetic phenotypes?

Objective: Nevirapine is an important component of highly active antiretroviral therapy used in the treatment of HIV infection. There is a considerable variation in the pharmacokinetics of nevirapine and this variation can impact the efficacy and toxicity of nevirapine. Although some of this variation can be attributed to environmental factors, the degree to which heritability influences nevirapine pharmacokinetics is unknown.

Elucidating the effect of final-day dosing of rifampin in induction studies on hepatic drug disposition and metabolism.

Because rifampin (RIF) induces hepatic enzymes and inhibits uptake transporters, dosing a drug that is a dual substrate of enzymes and uptake transporters on the final day of an inducing regimen should exhibit less inductive effect than dosing on the following day in the absence of RIF, since RIF decreases drug uptake into liver. In vitro and in vivo rat studies were conducted using digoxin as a model substrate. Digoxin was administered to an uninduced control group to obtain baseline values.