Review: Pharmacokinetics of illicit drugs in oral fluid

Oral fluid as an alternative matrix to monitor opiate and cocaine use in substance-abuse treatment patients

Interest in oral fluid as an alternative matrix for monitoring drug use is due to its ease-of-collection and non-invasiveness; however, limited data are available on the disposition of drugs into oral fluid. The objective of this research was to provide data on the presence and concentrations of heroin, cocaine and multiple metabolites in oral fluid after illicit opioid and cocaine use. Thrice weekly oral fluid specimens (N=403) from 16 pregnant opiate-dependent women were obtained with the Salivette oral fluid collection device. Evidence of heroin (N=62) and cocaine (N=130) use was detected in oral fluid by LC-APCI-MS/MS. 6-Acetylmorphine (6-AM), heroin and morphine were the major opiates detected, with median concentrations of 5.2, 2.3, and 7.5 microg/L, respectively. Cocaine and benzoylecgonine (BE) had median concentrations of 6.4 and 3.4 microg/L. Application of the Substance Abuse Mental Health Services Administration (SAMHSA) recommended cutoffs for morphine and codeine (40 microg/L), 6-AM (4 microg/L) and cocaine and BE (8 microg/L), yielded 28 opiate- and 50 cocaine-positive specimens. Oral fluid is a promising alternative matrix to monitor opiate and cocaine use in drug testing programs. These data guide interpretation of oral fluid test results and evaluate currently proposed SAMHSA oral fluid testing cutoffs.

The use of oral fluid for therapeutic drug management: clinical and forensic toxicology

One of the underlying tenets of clinical pharmacology is that only free drugs are pharmacologically active. It is thought that only free drugs can cross biological membranes to interact with a given receptor to alter its function, and that drug responses, both efficacious and toxic, are a function of unbound concentrations. The rationale for measuring drugs in oral fluid is that the free fraction of a drug in plasma reaches equilibrium with the drug in saliva. Although reports concerning the appearance of organic solutes in saliva have been in the literature for over 70 years, it has only been in the past 30 years that there has been emphasis on the appearance of drugs. Although many assumptions for drug level monitoring in saliva are made, the primary requisite for salivary monitoring to be useful is a constant or predictable relationship between the drug concentration in saliva and the drug concentration in plasma. Measurement of oral fluid drug levels for the purpose of managing patients and making dosage adjustments may be useful for select drugs or drug classes. However, it does not appear to be useful for the majority of drugs therapeutically monitored. Some work with antipsychotic medications has indicated that although the measurement of drug concentrations themselves may not be useful for dosage adjustment, the ratio of parent drug to metabolite may reflect altered metabolic status due to either pharmacogenetic variation or other clinical conditions. Furthermore, analysis of saliva may provide a cost-effective approach for the screening of large populations.

Drug Screening of Preserved Oral Fluid by Liquid Chromatography–Tandem Mass Spectrometry

Background: Oral fluid is an alternative matrix with potential applications in road-side drug screening, work-place testing, drug treatment programs, and epidemiological surveys. Development of methods for extensive drug screening in oral fluid is warranted.

Methods: We developed a liquid chromatography– tandem mass spectrometry (LC-MS/MS) method for drug screening of preserved oral fluid collected with the Intercept® collection device. Samples were prepared by liquid–liquid extraction with ethylacetate/heptane (4:1). LC-separation was achieved with an Atlantis dC18-column (2.1 × 50 mm, 3 μm particle). Mass detection was performed by positive ion mode electrospray LC-MS/MS and included the following drugs/metabolites: morphine, 6-monoacetylmorphine, codeine, buprenorphine, methadone, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxyethylamphetamine, cocaine, benzoylecgonine, Δ-9-tetrahydrocannabinol, lysergic acid diethylamide, alprazolam, bromazepam, clonazepam, 7-aminoclonazepam, diazepam, N-desmethyldiazepam, 3-OH-diazepam, fenazepam, flunitrazepam, 7-aminoflunitrazepam, lorazepam, nitrazepam, 7-aminonitrazepam, oxazepam, zopiclone, zolpidem, carisoprodol, and meprobamat.

Results: Screening of 32 drugs was performed with a run time of 14 min. Within- and between-day relative CVs varied from 2.0% to 31.8% and from 3.6% to 39.1%, respectively. Extraction recoveries were >50% except for morphine (30%) and benzoylecgonine (0.2%). The concentrations of the lowest calibrator were 1 nmol/L (0.28 μg/L) to 500 nmol/L (68 μg/L), depending on the drug.

Conclusion: The method allowed rapid and sensitive oral fluid screening for the most commonly abused drugs in Norway and will be used for a road-side survey of drug use in normal traffic.

Determination of midazolam and its hydroxy metabolites in human plasma and oral fluid by liquid chromatography/electrospray ionization ion trap tandem mass spectrometry

Midazolam (MDZ), a short-acting benzodiazepine, is a widely accepted probe drug for CYP3A phenotyping. Published methods for its analysis have used either therapeutic doses of MDZ, or, if employing lower doses, were mostly unable to quantify the two hydroxy metabolites. In the present study, a sensitive and specific liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantitative determination of MDZ and two of its metabolites (1'-hydroxymidazolam (1'-OHMDZ) and 4-hydroxymidazolam (4-OHMDZ)) in human plasma and oral fluid. After liquid-liquid extraction with hexane/dichloromethane (73:27, v/v), the analytes were separated on a Luna C18(2) (100 x 2.1 mm) analytical column using gradient elution. Detection was achieved using tandem mass spectrometry on an ion trap mass spectrometer. Midazolam-d6 was used as internal standard for quantification. The calibration curves were linear (R2 >0.998) between 0.05 and 20 ng/mL for MDZ and both metabolites in both matrices. Using 1 mL samples, the limit of detection was 0.025 ng/mL and the limit of quantification was 0.05 ng/mL for MDZ and the hydroxy metabolites in both matrices. Intra- and inter-day accuracies, determined at three different concentrations, were between 92.1 and 102.3% and the corresponding coefficients of variation were <7.3%. The average recoveries were 90.6%, 86.7% and 79.0% for MDZ, 1'-OHMDZ and 4-OHMDZ in plasma and 95.3%, 96.6% and 86.8% for MDZ, 1'-OHMDZ and 4-OHMDZ, respectively, in oral fluid. The method was successfully applied to a pharmacokinetic study, showing that MDZ and its hydroxy metabolites can be determined precisely in in vivo samples obtained following a single oral or intravenous dose of 2 mg MDZ. The method appears to be useful for CYP3A phenotyping in plasma using sub-therapeutic MDZ doses, but larger studies are needed to test this assumption.

Cognition and motor control as a function of Delta9-THC concentration in serum and oral fluid: limits of impairment

Cannabis use has been associated with increased risk of becoming involved in traffic accidents; however, the relation between THC concentration and driver impairment is relatively obscure. The present study was designed to define performance impairment as a function of THC in serum and oral fluid in order to provide a scientific framework to the development of per se limits for driving under the influence of cannabis. Twenty recreational users of cannabis participated in a double-blind, placebo-controlled, three-way cross-over study. Subjects were administered single doses of 0, 250 and 500 microg/kg THC by smoking. Performance tests measuring skills related to driving were conducted at regular intervals between 15 min and 6h post smoking and included measures of perceptual-motor control (Critical tracking task), motor impulsivity (Stop signal task) and cognitive function (Tower of London). Blood and oral fluid were collected throughout testing. Results showed a strong and linear relation between THC in serum and oral fluid. Linear relations between magnitude of performance impairment and THC in oral fluid and serum, however, were low. A more promising way to define threshold levels of impairment was found by comparing the proportion of observations showing impairment or no impairment as a function of THC concentration. The proportion of observations showing impairment progressively increased as a function of serum THC in every task. Binomial tests showed an initial and significant shift toward impairment in the Critical tracking task for serum THC concentrations between 2 and 5 ng/ml. At concentrations between 5 and 10 ng/ml approximately 75-90% of the observations were indicative of significant impairment in every performance test. At THC concentrations >30 ng/ml the proportion of observations indicative of significant impairment increased to a full 100% in every performance tests. It is concluded that serum THC concentrations between 2 and 5 ng/ml establish the lower and upper range of a THC limit for impairment.

Hyphenated mass spectrometric techniques-indispensable tools in clinical and forensic toxicology and in doping control

Hyphenated mass spectrometric techniques, particularly gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS), are indispensable tools in clinical and forensic toxicology and in doping control owing to their high sensitivity and specificity. They are used for screening, library-assisted identification and quantification of drugs, poisons and their metabolites, prerequisites for competent expertise in these fields. In addition, they allow the study of metabolism of new drugs or poisons as a basis for developing screening procedures in biological matrices, most notably in urine, or toxicological risk assessment. Concepts and procedures using GC/MS and LC/MS techniques in the areas of analytical toxicology and the role of mass spectral libraries are presented and discussed in this feature article. Finally, perspectives of their future position are discussed.

A validated gas chromatographic-electron impact ionization mass spectrometric method for methylenedioxymethamphetamine (MDMA), methamphetamine and metabolites in oral fluid

An analytical method to simultaneously quantify amphetamine (AMP), methamphetamine (MAMP), methylenedioxymethamphetamine (MDMA), methylenedioxyamphetamine (MDA), methylenedioxyethylamphetamine (MDEA), 3-hydroxy-4-methoxy-methamphetamine (HMMA) and 3-hydroxy-4-methoxy-amphetamine (HMA) in oral fluid is presented. Four hundred microlitres of oral fluid collected via expectoration was extracted by solid phase extraction. GC/MS-EI with selected ion monitoring (SIM) yielded linear curves 5-250 ng/mL for AMP, MAMP, MDMA and MDEA, 5-500 ng/mL for MDA and 25-1,000 ng/mL for HMA and HMMA. Recoveries were greater than 85%, accuracy 87-104%, and precision less than 8.3% coefficient of variation. This assay will be used to investigate distribution of sympathomimetic amines into human oral fluid following controlled drug administration.