Polyethylene glycol (PEG) molecules with 6 to 12 repeating units, used in the Ruma urine marker system, can suppress the signal of certain drugs during LC-MS/MS analysis, depending on their retention times. At a PEG concentration of 20 mcg/mL, the matrix effect fell below 60% for all drugs except nortilidine, and all drugs remained detectable. Quantification error was under 15% for drugs with deuterated internal standards and under 32% for those without. Sample preparation methods did not clearly reduce the effect, likely due to similar solubilities of PEGs and analytes.
The novel phenethylamines 4-fluoroamphetamine (4-FA) and 2,5-dimethoxy-4-bromophenethylamine (2C-B) are among the ten most used new psychoactive substances among high-risk users, and their use is also common in people with depression, ADHD, and those engaging in risky sexual behavior. A systematic review of literature on interactions between these phenethylamines and antidepressants, ADHD medications, and antiretrovirals found very limited pharmacokinetic data; only one case report suggested a possible interaction between 4-FA and ADHD medication. Pharmacodynamic profiles indicate potential interactions between both 4-FA and 2C-B with antidepressants and ADHD medications, primarily involving monoamine oxidases for both substances, with monoamine transporters more specific to 4-FA.