Oxytocin by intranasal and intravenous routes reaches the cerebrospinal fluid in rhesus macaques: determination using a novel oxytocin assay.

Oxytocin (OT) is a potential treatment for multiple neuropsychiatric disorders. As OT is a peptide, delivery by the intranasal (IN) route is the preferred method in clinical studies. Although studies have shown increased cerebrospinal fluid (CSF) OT levels following IN administration, this does not unequivocably demonstrate that the peripherally administered OT is entering the CSF. For example, it has been suggested that peripheral delivery of OT could lead to central release of endogenous OT. It is also unknown whether the IN route provides for more efficient entry of the peptide into the CSF compared to the intravenous (IV) route, which requires blood-brain barrier penetration. To address these questions, we developed a sensitive and specific quantitative mass spectrometry assay that distinguishes labeled (d5-deuterated) from endogenous (d0) OT. We administered d5 OT (80 IU) to six nonhuman primates via IN and IV routes as well as IN saline as a control condition. We measured plasma and CSF concentrations of administered and endogenous OT before (t=0) and after (t=10, 20, 30, 45 and 60 min) d5 OT dosing. We demonstrate CSF penetrance of d5, exogenous OT delivered by IN and IV administration. Peripheral administration of d5 OT did not lead to increased d0, endogenous OT in the CSF. This suggests that peripheral administration of OT does not lead to central release of endogenous OT. We also did not find that IN administration offered an advantage compared to IV administration with respect to achieving greater CSF concentrations of OT.

Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers.

Chronic cannabis (marijuana, hashish) smoking can result in dependence. Rodent studies show reversible downregulation of brain cannabinoid CB(1) (cannabinoid receptor type 1) receptors after chronic exposure to cannabis. However, whether downregulation occurs in humans who chronically smoke cannabis is unknown. Here we show, using positron emission tomography imaging, reversible and regionally selective downregulation of brain cannabinoid CB(1) receptors in human subjects who chronically smoke cannabis. Downregulation correlated with years of cannabis smoking and was selective to cortical brain regions. After ∼4 weeks of continuously monitored abstinence from cannabis on a secure research unit, CB(1) receptor density returned to normal levels. This is the first direct demonstration of cortical cannabinoid CB(1) receptor downregulation as a neuroadaptation that may promote cannabis dependence in human brain.

Biomarkers of Recent Cannabis Use in Blood, Oral Fluid and Breath.

Proving driving under the influence of cannabis (DUIC) is difficult. Establishing a biomarker of recent use to supplement behavioral observations may be a useful alternative strategy. We determined whether cannabinoid concentrations in blood, oral fluid (OF) or breath could identify use within the past 3 h-likely the period of the greatest impairment. In a randomized trial, 191 frequent (≥4/week) and occasional (<4/week) cannabis users smoked one cannabis (placebo [0.02%], or 5.9% or 13.4% Δ9-tetrahydrocannabinol [THC]) cigarette ad libitum. Blood, OF and breath samples were collected prior to and up to 6 h after smoking. Samples were analyzed for 10 cannabinoids in OF, 8 in blood and THC in breath. Frequent users had more residual THC in blood and were more likely to be categorized as 'recently used' prior to smoking; this did not occur in OF. Per se limits ranging from undetectable to 5 ng/mL THC in blood offered limited usefulness as biomarkers of recent use. Cannabinol (CBN, cutoff = 1 ng/mL) in blood offered 100% specificity but only 31.4% sensitivity, resulting in 100% positive predictive value (PPV) and 94.0% negative predictive value (NPV) at 4.3% prevalence; however, CBN may vary by cannabis chemovar. A 10 ng/mL THC cutoff in OF exhibited the overall highest performance to detect its use within 3 h (99.7% specificity, 82.4% sensitivity, 92.5% PPV and 99.2% NPV) but was still detectable in 23.2% of participants ∼4.4 h post-smoking, limiting specificity at later time points. OF THC may be a helpful indicator of recent cannabis intake, but this does not equate to impairment. Behavioral assessment of impairment is still required to determine DUIC. This study only involved cannabis inhalation, and additional research evaluating alternative routes of ingestion (i.e., oral) is needed.

THC and CBD blood and brain concentrations following daily administration to adolescent primates.

BACKGROUND: Cannabis availability with high concentrations of Δ-9-tetrahydrocannabinol (THC) and a range of THC to cannabidiol (CBD) ratios has increased in parallel with a rise in daily cannabis consumption by adolescents. Unanswered questions in adolescents include: 1) whether THC blood concentrations and THC metabolites remain stable or change with prolonged daily dosing, 2) whether CBD modulates THC pharmacokinetic properties and alters THC accumulation in brain, 3) whether blood THC levels reflect brain concentrations. METHODS: In adolescent squirrel monkeys (Saimiri boliviensis), we determined whether a four-month regimen of daily THC (1 mg/kg) or CBD (3 mg/kg) + THC (1 mg/kg) administration (IM) affects THC, THC metabolites, and CBD concentrations in blood or brain. RESULTS: Blood THC concentrations, THC metabolites and CBD remained stable during chronic treatment. 24 h after the final THC or CBD + THC injection, blood THC and CBD concentrations remained relatively high (THC: 6.0-11 ng/mL; CBD: 9.7-19 ng/mL). THC concentrations in cerebellum and occipital cortex were approximately twice those in blood 24 h after the last dose and did not significantly differ in subjects given THC or CBD + THC. CONCLUSIONS: In adolescent monkeys, blood levels of THC, its metabolites or CBD remain stable after daily dosing for four months. Our model suggests that any pharmacological interactions between CBD and THC are unlikely to result from CBD modulation of THC pharmacokinetics. Finally, detection of relatively high brain THC concentrations 24 h after the final dose of THC suggests that the prolonged actions of THC may contribute to persistent cognitive and psychomotor disruption after THC- or cannabis-induced euphoria wane.

Designer Drugs 2.0.

This "Designer Drugs 2.0" issue of Clinical Pharmacology & Therapeutics focuses on novel psychoactive substances, primarily cannabinoids and cathinones, and the repurposing of established psychoactive compounds (e.g., modafinil, psilocybin, lysergic acid diethylamide, and 3,4-methylenedioxymethamphetamine) that simultaneously offer new pharmacotherapies and pose serious health problems. Novel psychoactive substances were initially used as potent tools to investigate endogenous neurotransmitter systems; for example, synthetic cannabinoids have much higher potency than Δ9-tetrahydrocannabinol at the cannabinoid receptors. However, they are now being used illicitly as well as being tested for their efficacy in numerous clinical indications. Likewise, previously established psychoactive drugs are being repurposed as treatments for a wide variety of indications where currently approved medications are ineffective. This set of papers examines the arising problems associated with designer drugs (e.g., adverse events, psychosis, rapid new synthesis, abuse liability testing, internet sales, scheduling) as well as the potential therapeutic promises in areas as diverse as cognition enhancement, exercise-mimetics, epilepsy, multiple sclerosis, and posttraumatic stress disorder.

Approaches, Challenges, and Advances in Metabolism of New Synthetic Cannabinoids and Identification of Optimal Urinary Marker Metabolites.

We review approaches for determining metabolism of new synthetic cannabinoids (SCs), and challenges and advances in identifying optimal urinary marker metabolites of SC intake. Metabolic patterns of different SC generations are evaluated, and a practical strategy offered for selecting SC urinary marker metabolites. Novel SCs are incubated with human hepatocytes, the most abundant and characteristic metabolites are identified with high-resolution mass spectrometry, and proposed hepatocyte marker metabolites are confirmed in authentic positive urine samples.

Delayed emergence of methamphetamine's enhanced cardiovascular effects in nonhuman primates during protracted methamphetamine abstinence.

BACKGROUND: Methamphetamine abuse is linked with brain abnormalities, but its peripheral effects constitute an integral aspect of long-term methamphetamine use. METHODS: Eight male rhesus monkeys with long histories of intravenous methamphetamine self-administration were evaluated 1 day, and 1, 4, 12, 26, and 52 weeks after their last methamphetamine self-administration session. On test days, isoflurane-anesthetized animals received a 0.35 mg/kg IV methamphetamine challenge. A control group consisted of 10 age and gender matched drug naïve monkeys. Cardiovascular responses to methamphetamine were followed for 2.5h. Echocardiograms were acquired at 3 and 12 months of abstinence and in the control animals. RESULTS: No pre-methamphetamine baseline differences existed among 7 physiological measures across all conditions and controls. As expected, methamphetamine increased heart rate and blood pressure in controls. However, immediately following the self-administration period, the blood pressure response to methamphetamine challenge was reduced when compared to control monkeys. The peak and 150-min average heart rate increases, as well as peak blood pressure increases following methamphetamine were significantly elevated between weeks 12 to 26 of abstinence. These data indicate the development of tolerance followed by sensitization to methamphetamine cardiovascular effects. Echocardiography demonstrated decreased left ventricular ejection fraction and cardiac output at 3 months of abstinence. Importantly, both cardiovascular sensitization and cardiotoxicity appeared to be reversible as they returned toward control group levels after 1 year of abstinence. CONCLUSIONS: Enhanced cardiovascular effects may occur after prolonged abstinence in addicts relapsing to methamphetamine and may underlie clinically reported acute cardiotoxic events.

Neuropsychological performance in long-term cannabis users.

BACKGROUND: Although cannabis is the most widely used illicit drug in the United States, its long-term cognitive effects remain inadequately studied. METHODS: We recruited individuals aged 30 to 55 years in 3 groups: (1) 63 current heavy users who had smoked cannabis at least 5000 times in their lives and who were smoking daily at study entry; (2) 45 former heavy users who had also smoked at least 5000 times but fewer than 12 times in the last 3 months; and (3) 72 control subjects who had smoked no more than 50 times in their lives. Subjects underwent a 28-day washout from cannabis use, monitored by observed urine samples. On days 0, 1, 7, and 28, we administered a neuropsychological test battery to assess general intellectual function, abstraction ability, sustained attention, verbal fluency, and ability to learn and recall new verbal and visuospatial information. Test results were analyzed by repeated-measures regression analysis, adjusting for potentially confounding variables. RESULTS: At days 0, 1, and 7, current heavy users scored significantly below control subjects on recall of word lists, and this deficit was associated with users' urinary 11-nor-9-carboxy-Delta9-tetrahydrocannabinol concentrations at study entry. By day 28, however, there were virtually no significant differences among the groups on any of the test results, and no significant associations between cumulative lifetime cannabis use and test scores. CONCLUSION: Some cognitive deficits appear detectable at least 7 days after heavy cannabis use but appear reversible and related to recent cannabis exposure rather than irreversible and related to cumulative lifetime use.

Blockade of effects of smoked marijuana by the CB1-selective cannabinoid receptor antagonist SR141716.

BACKGROUND: SR141716, a recently developed CB1 cannabinoid receptor antagonist, blocks acute effects of Delta-9-tetrahydrocannabinol (THC) and other CB1 cannabinoid agonists in vitro and in animals. These findings suggest that CB1 receptors mediate many of the effects of marijuana, but this has not been evaluated in humans. METHODS: Sixty-three healthy men with a history of marijuana use were randomly assigned to receive oral SR141716 or a placebo in an escalating dose (1, 3, 10, 30, and 90 mg) design. Each subject smoked an active (2.64% THC) or placebo marijuana cigarette 2 hours later. Psychological effects associated with marijuana intoxication and heart rate were measured before and after antagonist and marijuana administration. RESULTS: Single oral doses of SR141716 produced a significant dose-dependent blockade of marijuana-induced subjective intoxication and tachycardia. The 90-mg dose produced 38% to 43% reductions in visual analog scale ratings of "How high do you feel now?" "How stoned on marijuana are you now?" and "How strong is the drug effect you feel now?" and produced a 59% reduction in heart rate. SR141716 alone produced no significant physiological or psychological effects and did not affect peak THC plasma concentration or the area under the time x concentration curve. SR141716 was well tolerated by all subjects. CONCLUSIONS: SR141716 blocked acute psychological and physiological effects of smoked marijuana without altering THC pharmacokinetics. These findings confirm, for the first time in humans, the central role of CB1 receptors in mediating the effects of marijuana.

Pharmacokinetics and metabolism of the plant cannabinoids, delta9-tetrahydrocannabinol, cannabidiol and cannabinol.

Increasing interest in the biology, chemistry, pharmacology, and toxicology of cannabinoids and in the development of cannabinoid medications necessitates an understanding of cannabinoid pharmacokinetics and disposition into biological fluids and tissues. A drug's pharmacokinetics determines the onset, magnitude, and duration of its pharmacodynamic effects. This review of cannabinoid pharmacokinetics encompasses absorption following diverse routes of administration and from different drug formulations, distribution of analytes throughout the body, metabolism by different tissues and organs, elimination from the body in the feces, urine, sweat, oral fluid, and hair, and how these processes change over time. Cannabinoid pharmacokinetic research has been especially challenging due to low analyte concentrations, rapid and extensive metabolism, and physicochemical characteristics that hinder the separation of drugs of interest from biological matrices--and from each other--and lower drug recovery due to adsorption of compounds of interest to multiple surfaces. delta9-Tetrahydrocannabinol, the primary psychoactive component of Cannabis sativa, and its metabolites 11-hydroxy-delta9-tetrahydrocannabinol and 11-nor-9-carboxy-tetrahydrocannabinol are the focus of this chapter, although cannabidiol and cannabinol, two other cannabinoids with an interesting array of activities, will also be reviewed. Additional material will be presented on the interpretation of cannabinoid concentrations in human biological tissues and fluids following controlled drug administration.

Characterization of the absorption phase of marijuana smoking.

Rapid blood collection, a paced smoking protocol and timely collection of physiologic and behavioral measures were used to characterize the absorption phase of marijuana smoking. Six healthy males smoked a single marijuana cigarette (placebo, 1.75%, or 3.55% delta-9-tetrahydrocannabinol) in a double-blind, randomized, Latin square study design. Rapid blood sampling with a continuous withdrawal pump allowed simultaneous collection with concurrent physiologic and behavioral measures. Mean plasma levels of 7.0 and 18.1 ng/ml delta-9-tetrahydrocannabinol were observed after the first inhalation of a 1.75% and 3.55% delta-9-tetrahydrocannabinol cigarette, respectively. Blood levels increased rapidly and peaked at 9 minutes, before initiation of the last puff sequence at 9.8 minutes. Three of six subjects reported increases in drug "liking" scores after the first puff, and all subjects responded by the second puff of a high dose cigarette. Significant increases in heart rate and diastolic blood pressure occurred shortly after peak blood levels. Previous studies have indicated that there is a substantial time delay between peak plasma levels of delta-9-tetrahydrocannabinol and drug-induced effects. This study showed that behavioral and physiologic effects appear concurrently or within minutes after the rapid appearance of delta-9-tetrahydrocannabinol in blood during marijuana smoking.

Amphetamine-induced toxicity in dopamine terminals in CD-1 and C57BL/6J mice: complex roles for oxygen-based species and temperature regulation.

In order to examine differential strain susceptibility to neurotoxic effects of amphetamine and to assess the potential role of superoxide radicals in amphetamine-induced dopaminergic damage, the drug was injected to mice with different levels of copper/zinc superoxide dismutase (Cu/Zn SOD) enzyme. Administration of amphetamine (10 mg/kg, i.p., given every 2 h, a total of four times) to wild-type CD-1 and C57BL/6J mice caused significant decreases in dopamine and 3,4-dihydroxyphenylacetic acid levels, in [(125)I]RTI-121-labeled dopamine transporters as well as a significant depletion in the concentration of dopamine transporter and vesicular monoamine transporter 2 proteins. The amphetamine-induced toxic effects were less prominent in CD-1 mice, which have much higher levels of Cu/Zn SOD activity (0.69 units/mg of protein) in their striata than C57BL/6J animals (0.007 units/mg of protein). Transgenic mice on CD-1 and C57BL/6J background, which had striatal levels of Cu/Zn SOD 2.57 and 1.67 units/mg of protein, respectively, showed significant protection against all the toxic effects of amphetamine. The attenuation of toxicity observed in transgenic mice was not caused by differences in amphetamine accumulation in wild-type and mutant animals. However, CD-1-SOD transgenic mice showed marked hypothermia to amphetamine whereas C57-SOD transgenic mice did not show a consistent thermic response to the drug. The data obtained demonstrate distinctions in the neurotoxic profile of amphetamine in CD-1 and C57BL/6J mice, which show some differences in Cu/Zn SOD activity and in their thermic responses to amphetamine administration. Thus, these observations provide evidence for possible complex interactions between thermoregulation and free radical load in the long-term neurotoxic effects of this illicit drug of abuse.

A study of peptide--peptide interaction by matrix-assisted laser desorption/ionization.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to study peptide-peptide interaction. The interaction was seen when 6-aza-2-thiothymine was used as a matrix (pH 5.4), but was disrupted with a more acidic matrix, alpha-cyano-4-hydroxycinnamic acid (pH 2.0). In the present study, we show that dynorphin, an opioid peptide, and five of its fragments that contain two adjacent basic residues (Arg6-Arg7), all interact noncovalently with peptides that contain two to five adjacent acidic residues (Asp or Glu). Two other nonrelated peptides containing two (Arg6-Arg7) or three (Arg1-Lys2-Arg3) adjacent basic amino acid residues were studied and exhibited the same behavior. However, peptides containing adjacent Lys or His did not form noncovalent complexes with acidic peptides. The noncovalent bonding was sufficiently stable that digestion with trypsin only cleaved Arg and Lys residues that were not involved in hydrogen bonding with the acidic residues. In an equimolar mixture of dynorphin, dynorphin fragments (containing the motif RR), and an acidic peptide (minigastrin), the acidic peptide preferentially complexed with dynorphin. If the concentration of minigastrin was increased 10 fold, noncovalent interaction was seen with dynorphin and all its fragments containing the motif RR. In the absence of dynorphin, minigastrin formed noncovalent complexes with all dynorphin fragments. These findings suggest that conformation, equilibrium, and concentration do play a role in the occurrence of peptide-peptide interaction. Observations from this study include: (1) ionic bonds were not disrupted by enzymatic digests, (2) conformation and concentration influenced complex formation, and (3) the complex did not form with fragments of dynorphin or unrelated peptides that did not contain the motifs RR or RKR, nor with a fragment of dynorphin where Arg7 was mutated to a phenylalanine residue. These findings strongly suggest that peptide-peptide interaction does occur, and can be studied by MALDI if near physiologic pH is maintained.

Acute and residual effects of marijuana: profiles of plasma THC levels, physiological, subjective, and performance measures.

Three experienced marijuana smokers participated in four 2-day experimental sessions in which they smoked either 0, 1, or 2 marijuana cigarettes containing 2.57% delta 9-tetrahydrocannabinol (THC) at two different times on the first day. A battery of physiological, subjective, and performance measures was repeated throughout day 1 to assess acute effects and on day 2 to measure any residual effects of marijuana. Blood samples were also repeatedly collected to examine the relationship between plasma levels and pharmacological effects of THC. Acutely, marijuana increased heart rate and subjective ratings of drug effects and slightly impaired performance on a circular lights task in all subjects. Performance was also impaired (decreased accuracy and increased response time) on serial addition/subtraction and digit recall tasks on day 1 in two subjects. On day 2, tachycardia and subjective effects of marijuana were not observed. Performance remained impaired on the arithmetic and recall tasks on day 2, although the decrements were not as large as those observed on day 1. In general, plasma THC levels covaried with the other measures. These preliminary results suggest that marijuana can adversely affect complex human performance up to 24 hours after smoking.

Differentiating new marijuana use from residual drug excretion in occasional marijuana users.

Increases in urine drug concentration that result from changes in urinary output may be mistakenly interpreted as new drug use rather than carryover from previous drug exposure. Normalization of drug excretion to urine creatinine concentration reduces the variability of drug measurement attributable to urine dilution. A specimen ratio of 1.5 or greater between two creatinine normalized positive urine cannabinoid tests was previously proposed as an indicator of new marijuana use. This approach has received wide attention for potential use in treatment and employee assistance programs associated with workplace drug testing. Unfortunately, there has been limited evaluation of the usefulness of this ratio under controlled-dosing conditions with marijuana smokers. A controlled clinical study was conducted to examine the excretion profile of creatinine and marijuana metabolites in a group of six marijuana users who smoked two different doses of marijuana over a 4-week period. A relative operating characteristic curve was constructed from sensitivity and specificity data for 26 different specimen ratios ranging from 0.1 to 2.0. The most accurate specimen ratio (85.4%) for differentiating new use from residual excretion was 0.5. Use of this ratio provided a sensitivity of 80.1%, a specificity of 90.2%, and 5.6% false-positive and 7.4% false-negative predictions. To substantiate the validity of the 0.5 specimen ratio, urine cannabinoid and creatinine data from a controlled clinical trial specifically addressing water dilution as a means of specimen adulteration were evaluated. Sensitivity, specificity, accuracy, and percent false-positive and percent false-negative predictions were 71.9%, 91.6%, 83.9%, 5.4%, and 10.7%, respectively. These data compared favorably with the results from the first clinical study, with the exception of slightly lower sensitivity and higher false-negative percentages in the water dilution study. This would be expected because of the ingestion of large amounts of water and consequent dilution of urine drug concentration. These data indicated that selection of a specimen ratio to evaluate sequential creatinine normalized urine drug concentrations can improve the ability to distinguish residual excretion from new marijuana usage. The selection of an appropriate specimen ratio can be made based on the needs of a specific urine drug-testing program taking into account sensitivity, specificity, and accuracy data.

Detection times of marijuana metabolites in urine by immunoassay and GC-MS.

Reports of prolonged drug excretion have provided the basis for the common assumption that cannabinoid metabolites may he detected in urine for a week or longer. The accuracy, sensitivity, and specificity of immunoassays for the detection of cannabinoids and metabolites are unique for a specific assay and may change overtime. it is important that individuals who select assays and those who interpret test results be aware of qualitative and quantitative changes that occur. In the present study, detection times of cannabinoids in urine were determined using cannabinoid immunoassays with 20-, 50-, and 100-ng/mL cutoffs and using gas chromatography-mass spectrometry (GC-MS). Six subjects each smoked a single marijuana cigarette (placebo, 1.75, or 3.55% delta9-tetrahydrocannabinol [THC]) each week while residing on the clinical ward of the Addiction Research Center. Each urine specimen was analyzed under blind conditions by immunoassay according to the manufacturer's instructions. The following cannabinoid reagents were evaluated: EMIT d.a.u. 100, EMIT d.a.u. 50, EMIT d.a.u. 20, EMIT II 100, EMIT II 50, Abuscreen OnLine, and Abuscreen RIA, DRI, and ADx. All urine specimens were also analyzed for 11-nor-9-carboxy-delta9-THC by GC-MS using a 15-ng/mL cutoff. Urinary cannabinoid detection times varied substantially across assays, subjects, doses, and cutoff concentrations. Detection times were shorter than previously assumed. Mean detection times increased from a maximum of 0.5 days after the low dose to 1.5 days after the high dose using the 100-ng/mL cutoff. Mean detection times were less than 1 day following the low dose and less than 2 days following high-dose exposure using the 50-ng/mL cutoff. Mean detection times ranged from 1 to 5 days after the low dose and from 3 to 6 days after the high dose using the 20-ng/mL cutoff immunoassay. GC-MS detection times were approximately twice as long as mean detection times using an immunoassay with a cutoff of 50 ng/mL. Differences in sensitivity and specificity between the available immunoassay products affected the efficiency of detection of marijuana use. These results indicate that recent reductions in cannabinoid cutoffs by military and federally mandated programs will increase detection times and improve sensitivity, as expected. However, monitoring acute marijuana usage with a commercial cannabinoid immunoassay that has a 50-ng/mL cutoff concentration provides only a narrow window of detection of 1-2 days.

Blood cannabinoids. I. Absorption of THC and formation of 11-OH-THC and THCCOOH during and after smoking marijuana.

delta 9-Tetrahydrocannabinol (THC), the primary psychoactive constituent of marijuana, is rapidly transferred from lungs to blood during smoking. Oxidative metabolism of THC yields the active metabolite, 11-hydroxy-delta 9-tetrahydrocannabinol (11-OH-THC), and the inactive metabolite, 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH). Characterization of THC's absorption phase is important because of the rapidity with which THC penetrates the central nervous system to produce psychoactive effects. This study incorporated a highly automated procedure to sample blood and to capture rapid drug level changes during and following smoking. Human subjects smoked one marijuana cigarette (placebo, 1.75%, or 3.55% THC) once a week according to a randomized, crossover, double-blind Latin square design. Samples were analyzed by GC/MS for THC, 11-OH THC, and THCCOOH. THC levels increased rapidly, peaked prior to the end of smoking, and quickly dissipated. Mean peak 11-OH-THC levels were substantially lower than THC levels and occurred immediately after the end of smoking. THCCOOH levels increased slowly and plateaued for an extended period. The mean peak time for THCCOOH was 113 min and a correspondingly longer time course of detection was observed. This study provides the first complete pharmacokinetic profile of the absorption of THC and appearance of metabolites during marijuana smoking. These findings have implications for understanding the mechanisms underlying the performance-impairing effects of marijuana, as well as for aiding forensic interpretation of cannabinoid blood levels.

Blood cannabinoids. II. Models for the prediction of time of marijuana exposure from plasma concentrations of delta 9-tetrahydrocannabinol (THC) and 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH)

Two mathematical models are described for the prediction of time of marijuana use from the analysis of a single plasma sample for cannabinoids. The models were derived from cannabinoid data obtained from a controlled clinical study of acute marijuana smoking. Model I was based on plasma delta 9-tetrahydrocannabinol (THC) concentrations and Model II was based on the ratio of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH) to THC in plasma. The two models were validated with cannabinoid data from nine published and unpublished clinical studies. The data included plasma samples obtained from infrequent and frequent marijuana smokers and after oral marijuana administration. Cannabinoid plasma concentrations had been determined by a variety of analytical methods. The accuracy of model prediction was evaluated by comparison of the predicted time of prior drug use to the actual time of exposure. Predictions of time of exposure were generally accurate but tended to overestimate time immediately after smoking and tended to underestimate later times. A second assessment of the validity of the models was made by determining if actual time of use was within the 95% confidence interval. Model I correctly predicted the time of exposure within the 95% confidence interval for 235 of 261 samples (90.0%), and Model II was correct in 232 of 260 samples (89.2%). These prediction models may be beneficial to forensic scientists in the interpretation of cannabinoid plasma levels.

Urinary excretion profiles of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol in humans after single smoked doses of marijuana.

Interpretation of marijuana-positive urine tests requires an understanding of the excretion pattern of marijuana metabolites in humans. However, limited urinary excretion data from controlled clinical studies of marijuana use are available. In this study, six subjects smoked a single marijuana cigarette (placebo, 1.75% delta 9-tetrahydrocannabinol [THC], or 3.55% THC) each week while residing on the clinical ward of the Addiction Research Center. Individual urine specimens were collected for 7 days after drug administration and analyzed for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH) by gas chromatography-mass spectrometry (GC-MS) with a limit of detection of 0.5 ng/mL. Substantial intersubject variability in patterns of THCCOOH excretion was noted between subjects and between doses. Mean THCCOOH concentrations in the first urine collections were 47 +/- 22.3 ng/mL and 75.3 +/- 48.9 ng/mL after the 1.75 and 3.55% THC cigarettes, respectively. Mean peak urine THCCOOH concentrations averaged 89.8 +/- 31.9 ng/mL and 153.4 +/- 49.2 ng/mL after smoking of approximately 15.8 mg and 33.8 mg THC, respectively. The mean times of peak urine concentration were 7.7 +/- 0.8 h after the 1.75% THC and 13.9 +/- 3.5 h after the 3.55% THC dose. Mean GC-MS THCCOOH detection times for the last positive urine sample after the smoking of a single 1.75 or 3.55% THC cigarette were 33.7 +/- 9.2 h and 88.6 +/- 9.5 h, respectively, when a 15-ng/mL cutoff concentration was used. An average of 93.9 +/- 24.5 micrograms THCCOOH (range, 34.6-171.6 micrograms) was excreted by each subject during the 7-day period after smoking of a single 1.75% THC cigarette. The average amount of THCCOOH excreted in the same time period after the high dose was 197.4 +/- 33.6 micrograms (range, 107.5-305.0 micrograms). This represented an average of only 0.54 +/- 0.14% and 0.53 +/- 0.09% of the original amount of THC in the low-and high-dose cigarettes, respectively. These data provide a detailed complication of THCCOOH concentrations in urine after administration of marijuana that may aid in the interpretation of urine cannabinoid results.

Cocaine and metabolite elimination patterns in chronic cocaine users during cessation: plasma and saliva analysis.

Several reports suggest a prolonged elimination of cocaine and metabolites after chronic use compared with single or occasional use. This study was designed to measure the half-lives of cocaine in plasma and saliva of individuals who consumed cocaine on a frequent basis. The disposition and elimination patterns of cocaine and metabolites in the body fluids of chronic high-dose cocaine users during acute cessation of use were investigated. Plasma and saliva specimens were collected over a 12-h period during cessation and analyzed by gas chromatography-mass spectrometry. Pharmacokinetic parameters were derived by noncompartmental analysis of plasma and saliva data. Results indicated a cocaine terminal T(1/2) of 3.8 h in plasma and 7.9 h in saliva. The terminal T(1/2) of benzoylecgonine was 6.6 h in plasma and 9.2 h in saliva. Compared with prior studies of acute low-dose cocaine administration, these findings suggest that cocaine's half-life is longer in active street users than in occasional users though the half-life of its main metabolite benzoylecgonine remains similar (as do cocaine saliva-to-plasma ratios). Thus, regular use of cocaine appears to alter the disposition and elimination of cocaine when compared to single or occasional use.