Fifty-three head hair specimens were collected from 38 males with a history of cannabis use documented by questionnaire, urinalysis and controlled, double blind administration of delta9-tetrahydrocannabinol (THC) in an institutional review board approved protocol. The subjects completed a questionnaire indicating daily cannabis use (N=18) or non-daily use, i.e. one to five cannabis cigarettes per week (N=20). Drug use was also documented by a positive cannabinoid urinalysis, a hair specimen was collected from each subject and they were admitted to a closed research unit. Additional hair specimens were collected following smoking of two 2.7% THC cigarettes (N=13) or multiple oral doses totaling 116 mg THC (N=2). Cannabinoid concentrations in all hair specimens were determined by ELISA and GCMSMS. Pre- and post-dose detection rates did not differ statistically, therefore, all 53 specimens were considered as one group for further comparisons. Nineteen specimens (36%) had no detectable THC or 11-nor-9-carboxy-THC (THCCOOH) at the GCMSMS limits of quantification (LOQ) of 1.0 and 0.1 pg/mg hair, respectively. Two specimens (3.8%) had measurable THC only, 14 (26%) THCCOOH only, and 18 (34%) both cannabinoids. Detection rates were significantly different (p<0.05, Fishers' exact test) between daily cannabis users (85%) and non-daily users (52%). There was no difference in detection rates between African-American and Caucasian subjects (p>0.3, Fisher's exact test). For specimens with detectable cannabinoids, concentrations ranged from 3.4 to >100 pg THC/mg and 0.10 to 7.3 pg THCCOOH/mg hair. THC and THCCOOH concentrations were positively correlated (r=0.38, p<0.01, Pearson's product moment correlation). Using an immunoassay cutoff concentration of 5 pg THC equiv./mg hair, 83% of specimens that screened positive were confirmed by GCMSMS at a cutoff concentration of 0.1 pg THCCOOH/mg hair.

Background: Knowing the time cannabis was last used is important for determining impairment in accident investigations and clinical evaluations. Two models for predicting time of last cannabis use from single plasma cannabinoid concentrations-model I, using ⌬ 9 -tetrahydrocannabinol (THC), and model II, using the concentration ratio of 11-nor-9-carboxy-THC (THCCOOH) to THC-were developed and validated from controlled drug administration studies. Objectives of the current study were to extend the validation by use of a large number of plasma samples collected after administration of single and multiple doses of THC and to examine the effectiveness of the models at low plasma cannabinoid concentrations. Methods: Thirty-eight cannabis users each smoked a 2.64% THC cigarette in the morning, and 30 also smoked a second cigarette in the afternoon. Blood samples (n ‫؍‬ 717) were collected at intervals after smoking, and plasma THC and THCCOOH concentrations measured by gas chromatography-mass spectrometry. Predicted times of cannabis smoking, based on each model, were compared with actual smoking times. Results: The most accurate approach applied a combination of models I and II. For all 717 plasma samples, 99% of predicted times of last use were within the 95% confidence interval, 0.9% were overestimated, and none were underestimated. For 289 plasma samples collected after multiple doses, 97% were correct with no underestimates. All time estimates were correct for 76 plasma

A previously recommended a method for detecting new cannabis use with creatinine-normalized 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) urine concentrations in periodically collected specimens for treatment, workplace and judicial drug testing applications is refined by considering the time interval between urine collections. All urine specimens were collected from six less-than-daily cannabis users who smoked placebo, 1.75%, and 3.55% THC cigarettes in randomized order, each separated by one week. Ratios (n = 24,322) were calculated by dividing each creatinine-normalized THCCOOH concentration (U2) by that of a previously collected specimen (U1). Maximum, 95% limit, and median U2/U1 ratios with 15 and 6 ng THCCOOH/mL cutoff concentrations, with and without new use between specimens, were calculated for each 24-h interval after smoking up to 168 h and are included in tables. These ratios decreased with increasing interval between collections providing improved decision values for determining new cannabis use. For example, with a 15 ng THCCOOH/mL cutoff concentration and no new use between specimens, the maximum, 95% limit, and median U2/U1 ratios were 3.05, 1.59, and 0.686, respectively, when the collection interval was ≤ 24 h and 0.215, 0.135, and 0.085 when it was 96–119.9 h.

A method is described for simultaneous determination of cyanide (CN) and thiocyanate (SCN) in human saliva, or oral fluid. SCN concentrations in body fluids appeared to be important in classifying patients as smokers or nonsmokers, in determining some clinical conditions, and in specimen validity testing in forensic drug testing. The human saliva samples were diluted and the anions were separated by an extractive alkylation technique. Tetrabutylammonium sulfate was used as phase-transfer catalyst and pentafluorobenzyl bromide as the derivatizing agent. The products were analyzed by a gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring method. 2,5-Dibromotoluene was used as internal standard for quantitation of CN and SCN in saliva. The calibration plot was linear over the concentration range from 1 to 100 micromol/L (0.026-2.60 microg/mL) for CN (R=0.9978) and 5 to 200 micromol/L (0.29-11.6 microg/mL) for SCN (R=0.9996). The method was used to examine 10 saliva specimens. The concentration ranged from 4.8 to 29 micromol/L (0.13-0.75 microg/mL) for CN and 293 to 1029 micromol/L (17-59.7 microg/mL) for SCN. The SCN results were similar to those obtained from a method using oxidation of SCN to CN with colorimetric detection (R=0.9882). The proposed GC-MS confirmatory method was found useful when the concentrations of CN and SCN in saliva needed to be accurately determined.

A weight-based UFH dosing nomogram using antifactor Xa monitoring resulted in a high percentage of patients achieving target antifactor Xa values within the first 24 hours of therapy.

No abstract

The sites of energy transduction within the human hemoglobin molecule for the regulation of oxygen affinity have been determined by an extensive study of the molecule's energetic response to structural alteration at individual amino acid residues. For 22 mutant and chemically modified hemoglobins we have determined the total free energy used by the tetrameric molecule for alteration ofoxygen affinity at the four binding steps. The results imply that the regulation of oxygen binding affinity is due to energy changes which are mostly localized at the a'(32 interface. They also indicate a high degree of "internal cooperativity" within this contact region-i.e., the structural perturbations at individual residue sites are energetically coupled. Cooperativity in ligand binding is thus a reflection of cooperativity at a deeper level-that of the protein-protein interactions within the al(92-interfacial domain.A fundamental problem of protein structure and function is the issue ofhow "local" properties ofindividual amino acid residues are related to "system" properties which reflect behavior ofthe molecule as a whole. Well-known manifestations ofthis problem include (a) the acid-base titration behavior of proteins, (b) the cooperative folding of tertiary structures, (c) the nucleated polymerization of self-assembling aggregates, and (d) the cooperative binding ofligands in allosteric systems. A large number of studies, including both experimental and theoretical work, have provided insights into the nature of these problems (cf. refs. 1-15).One strategy for the exploration ofstructure-energy coupling and its role in biological function lies in perturbing a protein molecule through alteration of individual amino acid residues (i.e., deletion, substitution, or chemical modification) and determining the effects of these alterations upon appropriately selected system properties. By studying the effects on the system properties ofa series of such changes, distributed throughout the molecular structure, one can determine which regions of the molecule are especially sensitive to structural perturbation. The power of this approach will be maximized when the system properties chosen reflect the energy states of the molecule as a whole and are at the same time directly related to its biological functions.In this paper we present results of such a study with human hemoglobin. Using 23 different hemoglobins we have determined the effects of structural perturbation upon the energy invested by-the molecule in altering the affinity at successive oxygenation steps. The results provide a structural "map" of energetic sensitivity related to the regulation of function.The problem of structure-energy correlation in the human hemoglobin molecule is centered on the classic problem of resolving the cooperative mechanism of oxygen binding. A complete understanding of this problem must include (a) the structural and energetic changes at the heme site that accompany the binding of oxygen, (b) the changes of tertiary structure and energy ...

Sweat testing is a noninvasive technique for monitoring drug exposure over a 7-day period in treatment, criminal justice, and employment settings. We evaluated Δ 9 -tetrahydrocannabinol (THC) excretion in 11 daily cannabis users after cessation of drug use. PharmChek ® sweat patches worn for 7 days were analyzed for THC by gas chromatography-mass spectrometry (GC/MS). The limit of quantification (LOQ) for the method was 0.4 ng THC/patch. Sweat patches worn the first week of continuously monitored abstinence had THC above the United States Substance Abuse Mental Health Services Administration's proposed cutoff concentration for federal workplace testing of 1 ng THC/patch. Mean ± S.E.M. THC concentrations were 3.85 ± 0.86 ng THC/patch. Eight of 11 subjects had negative patches the second week and one produced THC positive patches for four weeks of monitored abstinence. We also tested daily and weekly sweat patches from 7 subjects who were administered oral doses of up to 14.8 mg THC/day for five consecutive days. In this oral THC administration study, no daily or weekly patches had THC above the LOQ; concurrent plasma THC concentrations were all less than 6.1 μg/L. In conclusion, using proposed federal cutoff concentrations, most daily cannabis users will have a positive sweat patch in the first week after ceasing drug use and a negative patch after subsequent weeks, although patches may remain positive for four weeks or more. Oral ingestion of up to 14.8 mg THC daily does not produce a THC positive sweat patch test.