Laboratory Resource

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The need for analytical chemistry support for clinical studies arose because of increased appreciation of the importance of pharmacokinetics in understanding drug action in the late 1970s. Neal Benowitz had initiated pharmacokinetic studies of nicotine and opioids and Reese Jones initiated studies of cocaine pharmacokinetics and pharmacodynamics, largely supported by a P50 award. At that time, our analytical laboratory consisted of a chemist, two technicians and two gas chromatographs. Since, many projects requiring analytical chemistry support were initiated and our laboratory staff has grown from three to 14: Two PhD Research Chemists, nine Staff Research Associates and three Laboratory Assistants. Major equipment includes two gas chromatographs, two desktop GC-MS systems, two HPLCs, three triple-stage quadrupole LC-MS/MS systems, and two triple-stage quadrupole GC-MS/MS systems. Support for the laboratories comes from the P30 Center, ROIs and contracts. In recent years, our group has made extensive, and we believe innovative, use of stable isotope methodology. Stable isotope-labeled drugs, unlike those labeled with radioisotopes, are no more hazardous than unlabeled drugs. A stable isotope, such as the hydrogen isotope deuterium, incorporated into a drug molecule allows the labeled drug to be used as a tracer. This is a powerful tool in studies of pharmacokinetics and metabolism, frequently used in bioavailability studies. While the natural drug is administered by its usual route, such as oral, transdermal, or by smoking, the labeled drug is simultaneously administered intravenously for pharmacokinetic characterization. We have used this technique to determine nicotine intake from smoking (Benowitz et al. 1991a) and from smokeless tobacco (Jacob et al. 1999), bioavailability of transdermal nicotine (Benowitz et al. 1991b) and bioavailability of cocaine administered by various routes. We have used stable isotope methodology to study the metabolic disposition of cocaine and ethanol, including determination of the fractional conversion of cocaine to cocaethylene (Jacob et al. 1997; Everhart et al. 1998). Stable isotope methodology was used to determine the bioavailablity of intranasal and smoked methamphetamine (Harris et al. 2003). Our use of stable isotopes is continuing and expanding. We will be utilizing labeled frans-3'-hydroxycotinine to further our understanding of nicotine pharmacogenetics and to better understand the mechanism of racial differences in nicotine metabolism.. Cotinine-d4 and the metabolite ratio will be used to study the association of the rate of metabolism and development of addiction in adolescent light smokers (Mark Rubinstein, MD, CA140216). We have used stable isotope methodology to address questions unique to the drug abuse area. One such question was to determine whether intravenous nicotine replacement would suppress nicotine intake from smoking (Benowitz and Jacob 1990). This led to the conclusion that nicotine replacement medications such as transdermal patches (at that time undergoing premarketing clinical trials) would suppress smoking even if subjects were unable to quit entirely. We have used deuterium-labeled cocaine administration to study the time course of distribution of cocaine and its metabolite benzoylecgonine into human hair. For ethical reasons, these studies had to be carried out in cocaine abusers, and the use of labeled drug guaranteed that subsequent street cocaine use would not invalidate the results (Henderson et al. 1996). We are also using labeled nicotine to study the time course of accumulation of nicotine into hair and nails, which appear to be good long term biomarkers of nicotine exposure. Such studies require laboratories with synthetic and analytical chemists, and modern analytical instruments. Extensive use of mass spectrometry is necessary when using stable isotopes. Suitably labeled drugs or metabolites may not be commercially available, and our capability in synthetic organic chemistry has been needed to prepare stable-isotope labeled drugs, metabolites, and internal standards for clinical studies and assays. In this application, we are requesting support for laboratory, and administrative staff, and for instrumentation to maintain and enhance our analytical chemistry capabilities.