Preparation of Norcocaine

Synthesis, fluorine-18 radiolabeling, and biological evaluation of N-((E)-4-fluorobut-2-en-1-yl)-2beta-carbomethoxy-3beta-(4'-halophenyl)nortropanes: candidate radioligands for in vivo imaging of the brain dopamine transporter with positron emission tomography

The N-(E)-fluorobutenyl-3beta-(para-halo-phenyl)nortropanes 9-12 were synthesized as ligands of the dopamine transporter (DAT) for use as (18)F-labeled positron emission tomography (PET) imaging agents. In vitro competition binding assays demonstrated that compounds 9-12 have a high affinity for the DAT and are selective for the DAT compared to the serotonin and norepinephrine transporters. MicroPET imaging with [(18)F]9-[(18)F]11 in anesthetized cynomolgus monkeys showed high uptake in the putamen with lesser uptake in the caudate, but significant washout of the radiotracer was only observed for [(18)F]9. PET imaging with [(18)F]9 in an awake rhesus monkey showed high and nearly equal uptake in both the putamen and caudate with peak uptake achieved after 20 min followed by a leveling-off for about 10 min and then a steady washout and attainment of a quasi-equilibrium. During the time period 40-80 min postinjection of [(18)F]9, the ratio of uptake in the putamen and caudate vs cerebellum uptake was > or = 4.

Stability of Methylecgonidine and Ecgonidine in Sheep Plasma in Vitro

Background: Crack smokers are exposed to a pyrolysis product, methylecgonidine (MEG), which can be used as an analytical marker for crack smoking. Ecgonidine (EC), a hydrolytic product of MEG, has been identified in urine of crack smokers. MEG undergoes conversion to EC, complicating analysis and perhaps explaining a lack of forensic blood specimens containing MEG.

Methods: We developed gas chromatography–mass spectrometry (GC-MS) assays for MEG and EC. Plasma was collected from sheep blood containing 0, 0.06, or 0.24 mol/L (0%, 0.25%, or 1%) NaF. MEG was added to these plasmas, and they were incubated at −80, 1, 21, or 37 °C to determine whether there were temporal, temperature, or storage effects on MEG stability over 48 h.

Results: Decreased temperature and increased NaF concentrations limited MEG degradation and EC formation. MEG stored in plasma at −80 °C was stable up to 1 month, even in the absence of NaF.

Conclusions: MEG is stable in sheep plasma collected in commercially available, evacuated blood-collection tubes containing NaF and stored at −80 °C. In vitro formation of EC can be minimized with appropriate sample handling, and its in vivo formation may provide a better marker of crack smoking than its parent pyrolysis product.

Synthesis of 3 beta-aryl-8-azabicyclo[3.2.1]octanes with high binding affinities and selectivities for the serotonin transporter site

A novel entry to tropane analogs of cocaine was developed based on the reaction of rhodium-stabilized vinylcarbenoids with pyrroles. These analogs were tested in binding to dopamine, serotonin (5-HT), and norepinephrine transporters in membranes from rat striatum and frontal cortex. In all the analogs, the aryl group at the 3 position was directly bound to the tropane ring and an ethyl ketone moiety was present at the 2 position. By appropriate modification of the aryl and nitrogen substituents, highly potent and 5-HT selective tropanes were prepared. The most potent and selective compound was 3 beta-[4-(1-methylethenyl)phenyl]-2 beta-propanoyl-8-azabicyclo[3.2.1]octane (13b) which had a Ki of 0.1 nM at 5-HT transporters and was 150 times more potent at 5-HT vs dopamine transporters and almost 1000 times more potent at 5-HT vs norepinephrine transporters.

Effects of ethanol on cocaine metabolism: formation of cocaethylene and norcocaethylene

The coabuse of cocaine and ethanol occurs with high frequency and increases the risk of cocaine-related morbidity and mortality. The mechanisms mediating the toxic interactions of cocaine and ethanol are not clearly defined. This study examined the effects of acute ethanol administration on the metabolism of cocaine in the male Wistar rat. Intraperitoneal administration of 2 g/kg ethanol 30 min prior to administration of 25 mg/kg cocaine resulted in the formation of two ethylated derivatives of cocaine, benzoylecgonine ethyl ester (cocaethylene) and benzoylnorecgonine ethyl ester (norcocaethylene) in liver, brain, and serum. Fifteen minutes after cocaine administration, the tissue levels of cocaethylene were 22, 10, and 9% of the cocaine recovered from liver, serum, and brain, respectively. Ethanol pretreatment increased cocaine concentrations in liver and benzoylnorecgonine concentrations in liver and serum. The increased morbidity and hepatotoxicity seen with acute combined administration of cocaine and ethanol may be due to the formation of the toxic ethylated and N-demethylated metabolites of cocaine. Ethanol pretreatment decreased benzoylecgonine concentrations in serum and liver. The most important consequence of ethanol-induced inhibition of the normally rapid hydrolysis of cocaine to benzoylecgonine may be a decrease in benzoylecgonine-mediated vasoconstriction.

Determination of cocaine and selected metabolites in canine and human serum by reversed-phase high-performance liquid chromatography on coupled cyanopropyl and silica columns

A high-performance liquid chromatographic procedure for the determination of cocaine and selected metabolites (benzoylecgonine, norcocaine and benzoylnorecgonine) from human and canine serum has been developed. The analytes are extracted from 0.5-ml serum samples using strong cation-exchange and octadecylsilane solid-phase extraction columns. Chromatographic separation was accomplished on coupled cyanopropyl and silica columns using acetonitrile-6.25 mM phosphate buffer, pH 2.9 (80:20 v/v) as eluent and a flow-rate of 1.1 ml/min. Low-wavelength UV detection (228 nm, cadmium lamp) allowed detection of 1 ng/ml for each analyte. The assay was linear from 0 to 200 ng/ml (r2 = 0.997-0.999, n = 15 for each analyte) and showed good precision (relative standard deviation = 0.66-13.8%, n = 6) and accuracy (98-115% relative recovery).

A comparison of cocaine and its metabolite norcocaine: effects on locomotor activity

Intraventricular and intraperitoneal administration of cocaine and its metabolite norcocaine were studied in adult male rats. Norcocaine (10-100 micrograms) had no behavioral activity following central infusion but proved to be toxic at high doses (50-100 mg/kg) when given peripherally. Cocaine at high doses (100 micrograms), produced possible hypoactivity after central injections but produced significant hyperactivity after peripheral administration (20 mg/kg).

Biotransformation of norcocaine to norcocaine nitroxide by rat brain microsomes

In the mid 1970's, norcocaine was identified as a metabolite of cocaine in rat brain tissue. We extend these studies by demonstrating that rat brain FAD-containing monooxygenase metabolizes norcocaine to N-hydroxynorcocaine. This hydroxylamine is then further oxidized to the nitroxyl free radical norcocaine nitroxide by rat brain cytochrome P-450. Brain microsomal reduction of norcocaine nitroxide leads to the generation of superoxide. Finally, incubation of rat brain microsomes with either N-hydroxynorcocaine or norcocaine nitroxide leads to significant lipid peroxidation as monitored by spin-trapping techniques.