Phencyclidine metabolism: resolution, structure, and biological activity of the isomers of the hydroxy metabolite, 4-phenyl-4-(1-piperidinyl)cyclohexanol.

One of the major biotransformation pathways in the metabolism of phencyclidine is hydroxylation at C-4 of the cyclohexane ring to give 4-phenyl-4-(1-piperidinyl)cyclohexanol (1). Since the latter compound can exist as cis and trans isomers and the synthetic mixture has been reported to be biologically active, it was of interest to separate the isomers, test them for biological activity, and determine their ratio as metabolic products of phencyclidine. The synthetic mixture of 1 was separated by TLC and the individual isomers were characterized by 13C and 1H NMR and MS analyses. Preliminary testing of the isomers in the mouse rotarod assay indicates that the trans isomer (1b) is only slightly more active then the cis isomer (1a). Both isomers produced seizure activity and lethality at doses required to produce maximal ataxia.

Testing human hair for drugs of abuse. II. Identification of unique cocaine metabolites in hair of drug abusers and evaluation of decontamination procedures.

Two unique metabolites of cocaine, cocaethylene and norcocaine, were identified by GC/MS in the hair of cocaine users. Their presence cannot be explained by environmental contamination; thus, their presence together with cocaine provides convincing evidence that cocaine is excreted in hair after active cocaine administration. The amount of cocaine in hair predominated over all metabolites generally by a factor of 5-10. Two washing procedures were evaluated for their efficiency in removal of cocaine from environmentally contaminated hair. Neither procedure completely removed cocaine, suggesting that false positives can result from environmental contamination. Analysis of the methanolic wash of the hair of cocaine users also revealed the presence of cocaine metabolites, indicating that washing removes cocaine from the interior as well as from the exterior surface of hair during decontamination procedures.

Confirmation of cocaine in human saliva after intravenous use.

The presence of cocaine was confirmed in the saliva of two male human subjects who had received intravenous doses of cocaine. For one subject, the saliva:plasma concentration ratios varied from 2.96 to 0.5 over time following drug administration. Correlations of saliva to plasma cocaine levels were highly significant (p less than 0.001) across doses of 15, 20, and 40 mg of intravenously administered cocaine. These findings are important in that they allow monitoring blood levels of cocaine after intravenous infusion in a non-invasive manner, and could form the basis for development of a non-invasive screen for active cocaine levels in saliva.

Passive inhalation of cocaine.

Six healthy male volunteers were exposed to the vapor of 100 and 200 mg freebase cocaine heated to a temperature of 200 degrees C in an unventilated room (12,600-L volume) for a period of 1 h. No pharmacological effects were detected as a result of the exposure. Blood specimens collected immediately following exposure were negative for cocaine and metabolites. Urine specimens analyzed by gas chromatography-mass spectrometry contained peak concentrations of benzoylecgonine that ranged from 22 to 123 ng/mL. The peak excretion time for benzoylecgonine following passive exposure was approximately 5 h. The amount of cocaine inhaled by the subjects during passive exposure was estimated from room air measurements of cocaine to be approximately 0.25 mg. The total amount of cocaine (cocaine plus metabolites) excreted in urine by the six subjects ranged from 0.04 to 0.21 mg. For comparison, the six subjects also received an intravenous injection of 1 mg cocaine hydrochloride. Four of six subjects screened positive (300-ng/mL cutoff concentration) following the injection, indicating that the minimum amount of cocaine in these subjects necessary to produce positive results was approximately 1 mg. A second passive inhalation study was undertaken in which specimens were collected from research staff who assisted in a series of experimental studies with "crack" (freebase cocaine) smokers. The research staff remained in close vicinity while the crack smokers smoked three doses of freebase cocaine (12.5, 25, and 50 mg) over a period of 4 h. As a result, staff members were passively exposed to sidestream smoke from crack pipes and to breath exhalation from the crack smokers. Urine specimens from the staff members contained a maximum of 6 ng/mL benzoylecgonine. Only traces (less than 1 ng/mL) of cocaine were detected in any specimen. Overall, these studies demonstrated that individuals exposed to cocaine smoke under naturalistic or artificial conditions absorbed small amounts of cocaine that were insufficient to produce positive urine specimens at standard Department of Health and Human Services cutoffs. However, passive exposure conditions that would result in absorption of cocaine in amounts exceeding 1 mg could result in the production of cocaine-positive urine specimens.

Passive inhalation of marijuana smoke: urinalysis and room air levels of delta-9-tetrahydrocannabinol.

In two separate studies, 5 drug-free male volunteers with a history of marijuana use were passively exposed to the sidestream smoke of 4 and 16 marijuana cigarettes (2.8% delta-9-tetrahydrocannabinol [THC]) for 1 h each day for 6 consecutive days. A third study was similarly performed with 2 marijuana-naive subjects passively exposed to the smoke of 16 marijuana cigarettes. Passive smoke exposure was conducted in a small, unventilated room. Room air levels of THC and CO were monitored frequently. All urine specimens were collected and analyzed by EMIT d.a.u. assay, Abuscreen radioimmunoassay and GC/MS. The studies show that significant amounts of THC were absorbed by all subjects at the higher level of passive smoke exposure (eg., smoke from 16 marijuana cigarettes), resulting in urinary excretion of significant amounts of cannabinoid metabolites. However, it seems improbable that subjects would unknowingly tolerate the noxious smoke conditions produced by this exposure. At the lower level of passive marijuana-smoke exposure, specimens tested positive only infrequently or were negative. Room air levels of THC during passive smoke exposure appeared to be the most critical factor in determining whether a subject produced cannabinoid-positive urine specimens.

Validity testing of commercial urine cocaine metabolite assays: IV. Evaluation of the EMIT d.a.u. cocaine metabolite assay in a quantitative mode for detection of cocaine metabolite.

The EMIT d.a.u. cocaine metabolite assay (EMIT dau) was evaluated in a quantitative mode for analysis of clinical specimens obtained after controlled cocaine administration to human subjects. The quantitative results showed high concordance with those of gas chromatography/mass spectrometry (GC/MS) assays of the same specimens for benzoylecgonine, and no false positive or false negative results were obtained. The evaluation also included analysis of standardized solutions containing benzoylecgonine, cocaine, and other cocaine metabolites and isomers. The EMIT dau antibody demonstrated high selectivity for benzoylecgonine. The precision was somewhat less than that reported earlier for other commercial cocaine metabolite immunoassays. Quantitation of initial screening results from EMIT dau testing can serve as a useful guide for confirmation by GC/MS in forensic science urine testing.

Physiologic effects and plasma kinetics of beta-phenylethylamine and its N-methyl homolog in the dog.

Single i.v. doses of beta-phenylethylamine (PEA) and its N-methyl homolog (NMPEA) were administered to separate groups of five dogs. The dose- and time-related effects of these compounds were determined on pupil diameter, heart rate and body temperature. Blood samples were obtained concurrently with the physiologic measures and plasma levels of PEA and NMPEA were determined by gas chromatography. Both compounds dilated pupils, tended to produce an initial tachycardia followed by a bradycardia and elevated body temperature. The plasma pharmacokinetics of both PEA and NMPEA could be described by first-order kinetics which estimated half-lives of approximately 5 to 10 min. Plasma levels for both amines correlated significantly only with increases in pupil diameter. The present findings demonstrate that the endogenous trace amine PEA and NMPEA, which may be produced enzymatically by nonspecific N-methyl transferases, produce prominent physiologic effects of short duration when administered i.v. in the dog, suggesting that alterations in the metabolism of these amines which result in elevated plasma levels can produce pronounced effects on mammalian nervous system function.

Physiologic effects and plasma kinetics of phenylethanolamine and its N-methyl homolog in the dog.

Single i.v. doses of the endogenous trace amine phenylethanolamine (PEOH) and its N-methyl homolog (NMPEOH) were administered to separate groups of five dogs. The dose- and time-related effects of these compounds were measured on pupillary diameter, heart rate and body temperature. Blood samples were obtained concurrently with the physiologic measures and plasma levels of PEOH and NMPEOH were determined by gas chromatography. Both compounds dilated pupils, decreased heart rate and tended to lower body temperature. NMPEOH was approximately 1.25 times more potent than PEOH in dilating pupils. The plasma pharmacokinetics of both PEOH and NMPEOH could be described by a biexponential function with half-lives for the elimination phase of approximately 30 to 60 min. Plasma levels correlated significantly with increases in pupil diameter for both drugs, but only plasma levels of NMPEOH correlated significantly with changes in heart rate or body temperature. The present findings demonstrate that the endogenous trace amine PEOH and its N-methyl homolog NMPEOH, which may be produced endogenously by the enzymatic action of phenylethanolamine-N-methyl-transferase, produce prominent physiologic effects when administered i.v. in the dog, thus suggesting they may have physiologic roles in mammalian nervous system function.

Simultaneous determination of phencyclidine and monohydroxylated metabolites in urine of man by gas chromatography-mass fragmentography with methane chemical ionization.

Phencyclidine and monohydroxy metabolites were measured in human urine using gas chromatography-mass fragmentography with methane chemical ionization. Samples were extracted either untreated or following acid hydrolysis, derivatized with heptafluorobutyric anhydride, separated on a 3% SE-30 column and analyzed by mass fragmentography. The assay was sensitive to ca. 0.01 microgram/ml for phencyclidine and ca. 0.05 microgram/ml for the metabolites. Urine samples from five human subjects enrolled in a methadone maintenance program who had ingested phencyclidine were analyzed. The phencyclidine concentration ranged from 0.3 to 23.7 microgram/ml. The concentrations of metabolites ranged from 0 to 1.8 microgram/ml. A new monohydroxy metabolite was detected in the samples, but its structure was not fully elucidated. The specificity of the assay was examined.

63Ni electron-capture gas chromatographic assay for buprenorphine and metabolites in human urine and feces.

A 63Ni electron-capture gas chromatographic assay is described for buprenorphine, a potent narcotic agonist--antagonist. In addition, the assay is useful for the measurement of the metabolite norbuprenorphine and demethoxybuprenorphine, a rearrangement product resulting when buprenorphine is exposed to acid and heat. An extraction procedure was developed which optimized recovery of buprenorphine from biological samples and produced minimal background interferences and emulsion problems. Extract residues were derivatized with pentafluoropropionic anhydride and assayed by gas chromatography. Samples were analyzed with and without enzyme hydrolysis, thus providing a selective and sensitive assay for both free and conjugated buprenorphine, norbuprenorphine and demethoxybuprenorphine. The lower limits of detection following extraction of a 1-ml sample were ca. 10 ng/ml for buprenorphine and demethoxybuprenorphine and 5 ng/ml for norbuprenorphine. Application of the assay to human samples following a 40-mg oral dose of buprenorphine produced no evidence for the presence of demethoxybuprenorphine in urine or feces. Norbuprenorphine (free and conjugated) was present in urinary and fecal samples; buprenorphine (free and conjugated) was found in high amounts only in feces and in trace amounts in urine as conjugated buprenorphine. The urinary and fecal excretion pattern observed for a human subject following oral dosing of buprenorphine suggests enterohepatic circulation of buprenorphine.

The metabolism and excretion of buprenorphine in humans.

Buprenorphine, a powerful mixed agonist-antagonist analgesic which shows promise of providing maintenance pharmacotherapy for heroin addicts, is metabolized in male human subjects to norbuprenorphine and to conjugated buprenorphine and norbuprenorphine. Following subcutaneous, sublingual, and oral buprenorphine administration to a single subject, total metabolite excretion in urine was 2, 13.4, and 12.1%, respectively. No free parent drug was detected in urine. The amount of norbuprenorphine metabolite excreted in urine generally exceeded that of conjugated buprenorphine. In contrast, free and conjugated buprenorphine equaled or greatly exceeded total norbuprenorphine content in fecal samples following oral or sublingual administration. The greatest amount of drug and metabolite eliminated in feces occurred at 4 to 6 days following buprenorphine administration at times when there was very little urinary excretion of conjugated buprenorphine. This latter evidence indicates an enterohepatic circulation of buprenorphine in humans.