Prescription Compliance or Illicit Designer Drug Abuse?

Abstract

A 62-year-old Caucasian woman underwent evaluation for possible liver transplantation. She had end-stage cirrhosis secondary to hepatitis C and alcohol abuse. Among the tests ordered were urine screens for various drugs of abuse, including amphetamines, for which the patient's urine sample was positive. Given the patient's history of alcohol abuse and possible other drug abuse, her physicians questioned her in detail about recent use of any illicit substances. The patient stated emphatically that she had used no recreational drugs for the past 15 years. The physicians wondered what could be the cause of a false-positive result and relayed to the laboratory that the patient was on several medications. The laboratory arranged to have the initial sample analyzed for amphetamines by GC-MS. The result was reported as negative for amphetamine, methamphetamine, 3,4-methylenedioxy-methamphetamine (MDMA),3 and 3,4-methylenedioxy-amphetamine (MDA). In addition, the laboratory contacted the manufacturer of the screening immunoassay used [Amphetamines II, a kinetic interaction of microparticles in solution (KIMS) assay; Roche Diagnostics] and was informed that the medications that the patient had been prescribed, namely trazodone and bupropion, had been tested and did not exhibit any cross-reactivity. Amphetamines are a group of compounds that include amphetamine, methamphetamine, MDMA, and a large number of “designer drugs.” Widespread abuse has been reported worldwide and has increased over the last decade (1). In the clinical laboratory, the detection of amphetamine abuse has become increasingly important because of the potential for adverse drug–drug interactions involving existing prescription pharmaceuticals. Many antidepressants and antipsychotics function by affecting concentrations of dopamine, norepinephrine, and/or serotonin. Likewise, amphetamines increase concentrations of these biogenic amines by blocking their uptake by plasma membrane and/or vesicular transporters. Thus, in addition to their well-documented habit-forming properties and toxicities (2), amphetamines are of concern to clinicians because of their potentially toxic or fatal drug–drug interactions …