Physiologically based pharmacokinetic modeling to predict the pharmacokinetics of codeine in different CYP2D6 phenotypes

Objectives

Codeine, a prodrug used as an opioid agonist, is metabolized to the active product morphine by CYP2D6. This study aimed to establish physiologically based pharmacokinetic (PBPK) models of codeine and morphine and explore the influence of CYP2D6 genetic polymorphisms on the pharmacokinetics of codeine and morphine.

Methods

An initial PBPK modeling of codeine in healthy adults was established using PK-Sim® software and subsequently extrapolated to CYP2D6 phenotype-related PBPK modeling based on the turnover frequency (Kcat) of CYP2D6 for different phenotype populations (UM, EM, IM, and PM). The mean fold error (MFE) and geometric mean fold error (GMFE) methods were used to compare the differences between the predicted and observed values of the pharmacokinetic parameters to evaluate the accuracy of PBPK modeling. The validated models were then used to support dose safety for different CYP2D6 phenotypes.

Results

The developed and validated CYP2D6 phenotype-related PBPK model successfully predicted codeine and morphine dispositions in different CYP2D6 phenotypes. Compared with EMs, the predicted AUC0-∞ value of morphine was 98.6% lower in PMs, 60.84% lower in IMs, and 73.43% higher in UMs. Morphine plasma exposure in IMs administered 80 mg of codeine was roughly comparable to that in EMs administered 30 mg of codeine. CYP2D6 UMs may start dose titration to achieve an optimal individual regimen and avoid a single dose of over 20 mg. Codeine should not be used in PMs for pain relief, considering its insufficient efficacy.

Conclusion

PBPK modeling can be applied to explore the dosing safety of codeine and can be helpful in predicting the effect of CYP2D6 genetic polymorphisms on drug-drug interactions (DDIs) with codeine in the future.

Recent advances of drugs monitoring in oral fluid and comparison with blood

The use of alternative matrices in toxicological analyses has been on the rise in clinical and forensic settings. Oral fluid (OF), as non-invasive fluid, has attracted attention in the field of drug screening, both for therapeutic and forensic purposes, as well as for medical diagnosis, clinical management, on-site (real time) doping and for monitoring environmental exposure to toxic substances. A good correlation between OF and blood is now established for drug concentrations. Therefore, OF might be a potential substitute of blood, especially for long-term surveillance (e.g., therapeutic drugs) or to screen a large number of patients, as well as for the development of salivary point-of-care technologies. In this review, we aimed to summarize and critically evaluate the current literature that focused on the comparison of drugs detection in OF and blood specimens.

Adapting physiologically-based pharmacokinetic models for machine learning applications

Both machine learning and physiologically-based pharmacokinetic models are becoming essential components of the drug development process. Integrating the predictive capabilities of physiologically-based pharmacokinetic (PBPK) models within machine learning (ML) pipelines could offer significant benefits in improving the accuracy and scope of drug screening and evaluation procedures. Here, we describe the development and testing of a self-contained machine learning module capable of faithfully recapitulating summary pharmacokinetic (PK) parameters produced by a full PBPK model, given a set of input drug-specific and regimen-specific information. Because of its widespread use in characterizing the disposition of orally administered drugs, the PBPK model chosen to demonstrate the methodology was an open-source implementation of a state-of-the-art compartmental and transit model called OpenCAT. The model was tested for drug formulations spanning a large range of solubility and absorption characteristics, and was evaluated for concordance against predictions of OpenCAT and relevant experimental data. In general, the values predicted by the ML models were within 20% of those of the PBPK model across the range of drug and formulation properties. However, summary PK parameter predictions from both the ML model and full PBPK model were occasionally poor with respect to those derived from experiments, suggesting deficiencies in the underlying PBPK model.

Analysis of 2,5-dimethoxy-amphetamines and 2,5-dimethoxy-phenethylamines aiming their determination in biological matrices: a review

PURPOSE

The present review aims to provide an overview of methods for the quantification of 2,5-dimethoxy-amphetamines and -phenethylamines in different biological matrices, both traditional and alternative ones.

METHODS

A complete literature search was carried out with PubMed, Scopus and the World Wide Web using relevant keywords, e.g., designer drugs, amphetamines, phenethylamines, and biological matrices.

RESULTS

Synthetic phenethylamines represent one of the largest classes of "designer drugs", obtained through chemical structure modifications of psychoactive substances to increase their pharmacological activities. This practice is also favored by the fact that every new synthetic compound is not considered illegal by existing legislation. Generally, in a toxicological laboratory, the first monitoring of drugs of abuse is made by rapid screening tests that sometimes can occur in false positive or false negative results. To reduce evaluation errors, it is mandatory to submit the positive samples to confirmatory methods, such as gas chromatography or liquid chromatography combined to mass spectrometry, for a more specific qualitative and quantitative analysis.

CONCLUSIONS

This review highlights the great need for updated comprehensive analytical methods, particularly when analyzing biological matrices, both traditional and alternative ones, for the search of newly emerging designer drugs.

An Assessment of Occasional Bio-Inequivalence for BCS1 and BCS3 Drugs: What are the Underlying Reasons?

Despite having adequate solubility properties, bioequivalence (BE) studies performed on immediate release formulations containing BCS1/3 drugs occasionally fail. By systematically evaluating a set of 17 soluble drugs where unexpected BE failures have been reported and comparing to a set of 29 drugs where no such reports have been documented, a broad assessment of the risk factors leading to BE failure was performed. BE failures for BCS1/3 drugs were predominantly related to changes in C_max rather than AUC. C_max changes were typically modest, with minimal clinical significance for most drugs. Overall, drugs with a sharp plasma peak were identified as a key factor in BE failure risk. A new pharmacokinetic term (t½C_max) is proposed to identify drugs at higher risk due to their peak plasma profile shape. In addition, the analysis revealed that weak acids, and drugs with particularly high gastric solubility are potentially more vulnerable to BE failure, particularly when these features are combined with a sharp C_max peak. BCS3 drugs, which are often characterised as being more vulnerable to BE failure due to their potential for permeation and transit to be altered, particularly by excipient change, were not in general at greater risk of BE failures. These findings will help to inform how biowaivers may be optimally applied in the future.

Development and validation of quantitative analytical method for 50 drugs of antidepressants, benzodiazepines and opioids in oral fluid samples by liquid chromatography–tandem mass spectrometry

Purpose

We developed and validated a method for quantitative analysis of 50 psychoactive substances and metabolites (antidepressants, benzodiazepines and opioids) in oral fluid samples using simple liquid–liquid extraction procedure followed by liquid chromatography–tandem mass spectrometry (LC–MS/MS).

Method

Oral fluid samples were collected using Quantisal™ device and extracted by liquid–liquid extraction with 1.0 mL of methyl tert-butyl ether and then analyzed using LC–MS/MS.

Results

The method attended method validation criteria, with limits of quantification as low as 0.5 and 1.0 ng/mL, and linearity between 0.5–50.0 ng/mL for antidepressants, 0.5–25.0 ng/mL for benzodiazepines and 1.0–50.0 ng/mL to opioids. During method validation, bias and imprecision values were not greater than 16 and 20%, respectively. Ionization suppression/enhancement bias results were not greater than 25%. No evidence of carryover was observed. Sample stability studies showed that almost all analytes were stable at 25 °C for 3 days and at 4 °C for 7 days. Freeze–thaw cycles stability showed that most antidepressants and opioids were stable under these conditions. Autosampler stability study showed that all analytes were stable for 24 h, except for nitrazepam and 7-aminoclonazepam. Thirty-eight authentic oral fluid samples were analyzed; 36.8% of the samples were positive for 2 drugs. Citalopram was the most common drug found, followed by venlafaxine.

Conclusions

The method was validated according to international recommendations for the 50 analytes, showing low limits of quantification, good imprecision and bias values, using simple liquid–liquid extraction, and was successfully applied to authentic oral fluid samples analysis.

Entrapment of drugs in dental calculus - Detection validation based on test results from post-mortem investigations

For prospective investigation of drugs and metabolites in archaeological and contemporary dental calculus, a sensitive, broadly applicable ultra-high-performance liquid chromatography-tandem mass spectrometry method using pneumatically assisted electrospray ionisation (UHPLC-ESI-MS/MS) was developed. The dental calculus was treated with citric acid and the dissolution extracts were cleaned using weak and strong polymeric cation-exchange sorbents. The method was validated on hydroxyapatite for the analysis of 67 drugs and metabolites. Typically, the lower limits of quantification were in the range of 0.01-0.05ng for the sample mass extracted. The general applicability of the method was tested using dental calculus material sampled from 10 corpses undergoing forensic autopsy. The calculus material was washed several times before dissolution to remove residual substances originating from saliva, gingival crevicular fluid and blood. The wash extracts and the calculus samples (cleaned calculus material) were analysed using the same instrumental conditions. The dry mass of the calculus samples ranged from 1 to 10mg. The total number of drug detections was 131 in the dental calculus samples and 117 in the whole blood samples. From the analyses of the wash extracts and calculus samples, it was proven that drug residues were trapped in the interior of the calculus material. In 82 of the drug detections, the drug concentrations were higher in the dental calculus than in the blood. Among substances detected in the dental calculus but not in the blood were cocaine, heroin, 6-MAM and THCA-A.

Evaluation of Latent Fingerprints for Drug-Screening In A Social Care Setting

Sweat deposited via Latent Fingerprints (LFPs) was previously used to detect cocaine, opioids, cannabis and amphetamine via a point-of-care test (POCT). This screening method combined non-invasive sampling with a rapid result turnaround to produce a qualitative result outside of the laboratory. We report the novel application of a LFP drug screening test in a social care setting. Clients were tested on either an ad-hoc or routine basis using the POCT DOA114 (Intelligent Fingerprint Ltd.) drug screening cartridge. Screening cut-off values were 45, 35 and 95 pg/fingerprint for benzoylecgonine (BZE), morphine and amphetamine analytes, respectively. Confirmation LFP samples (DOA150, Intelligent Fingerprinting Ltd.) and oral fluid (OF) were analysed using UPLC-MS/MS. Thirty-six clients aged 36 ± 11 years participated (53% females). Individuals self-reported alcohol consumption (39%) and smoking (60%). Of 131 screening tests collected over 8 weeks: 14% were positive for cocaine; 2% for opioids; 1% amphetamine. Polydrug use was indicated in 10% of tests. Of 32 LFP confirmation tests, 63% were positive for cocaine and BZE. Opioids were also detected (31%) with the metabolite 6-monoacetylmorphine (6-MAM) being the most common (16%). In OF, cocaine was the dominant analyte (9%) followed 6-MAM (5%). Comparing positive LFP screening tests with positive OF samples found 39% and 38% were cocaine and opiate positive respectively. Out of the drugs screened for via the LFP POCT, cocaine was the most prevalent analyte in LFP and OF confirmation samples. The study is a step change in the routine drug screening procedures in a social care setting: especially useful for on-site cocaine detection in clients whose drug use was being monitored. Additionally, testing was easily accepted by clients and social care workers.

Resolving Issues About Efficacy and Safety of Low-Dose Codeine in Combination Analgesic Drugs: A Systematic Review

INTRODUCTION

The objective of this systematic review is to reflect on assumptions in relation to codeine use in combination with other analgesics.

METHODS

MEDLINE was searched according to the predetermined keywords and criteria. Only English language studies were taken into consideration and the outcome data of the final studies were extracted by two reviewers independently from each other and were checked by the third reviewer. Additionally, the available codeine-related Individual Case Safety Reports (ICSRs) retrieved from EudraVigilance were reviewed.

RESULTS

Sixteen placebo-controlled studies that involved 3378 subjects suffering from acute pain were analyzed for the efficacy of low-dose codeine (≤ 30 mg) combination products. Twelve of them found low-dose codeine combinations more efficient in relieving pain than the assigned comparator. According to 20 randomized clinical trials which included at least one dose of codeine (from 30 to 240 mg daily), the vast majority of reported side-effects were mild or moderate in severity. A total of 20 ICSRs for dependence were identified in the EudraVigilance database with codeine as a suspect drug for the 10-year time period for the European region.

CONCLUSIONS

Low-dose codeine combinations are effective after a single application in treating acute pain. Codeine in doses ≤ 30 mg and higher was considered safe since only mild to moderate side-effects were observed. There is no indication in the available sources which clearly links low doses of codeine to substance use disorder in non-dependent subjects.

Oral Fluid Drug Testing: Analytical Approaches, Issues and Interpretation of Results

With advances in analytical technology and new research informing result interpretation, oral fluid (OF) testing has gained acceptance over the past decades as an alternative biological matrix for detecting drugs in forensic and clinical settings. OF testing offers simple, rapid, non-invasive, observed specimen collection. This article offers a review of the scientific literature covering analytical methods and interpretation published over the past two decades for amphetamines, cannabis, cocaine, opioids, and benzodiazepines. Several analytical methods have been published for individual drug classes and, increasingly, for multiple drug classes. The method of OF collection can have a significant impact on the resultant drug concentration. Drug concentrations for amphetamines, cannabis, cocaine, opioids, and benzodiazepines are reviewed in the context of the dosing condition and the collection method. Time of last detection is evaluated against several agencies' cutoffs, including the proposed Substance Abuse and Mental Health Services Administration, European Workplace Drug Testing Society and Driving Under the Influence of Drugs, Alcohol and Medicines cutoffs. A significant correlation was frequently observed between matrices (i.e., between OF and plasma or blood concentrations); however, high intra-subject and inter-subject variability precludes prediction of blood concentrations from OF concentrations. This article will assist individuals in understanding the relative merits and limitations of various methods of OF collection, analysis and interpretation.

Cold water extraction of codeine/paracetamol combination products: a case series and literature review

Introduction: Tampering with opioid containing medications for use other than their prescribed indication is well documented; however, the published literature has concentrated on stronger, prescription opioids. Less potent opioids, such as codeine, are available without prescription in many European countries in the form of combination analgesic products and these can also be altered, with reports in particular of "cold-water extraction" being a tampering method achievable using household kitchen equipment.Methods: We searched a database of patients attending two South London emergency departments for cases of self-reported ingestion of the products of cold-water extraction, with subsequent review of their case notes. We searched the scientific and grey literature to identify current knowledge of this technique.Results: We identified seven presentations in six patients, none of whom developed paracetamol toxicity or had concentrations suggesting ingestion of a significant dose of paracetamol. A review of the scientific literature on the method also demonstrated that the technique reduces recovered paracetamol in experimental laboratory settings. Additionally, the established literature characterizes the use of codeine in a recreational setting and reports one fatality associated with the method. Review of grey literature user-forums further describes recreational codeine use in relation to the method and frequent adverse events including hospital admission for paracetamol toxicity.Discussion: Whilst the method appears capable of providing a recreational dose of codeine with reduction in the recovered paracetamol, it cannot be considered safe. Pharmaceutical production methods have been successfully developed to prevent tampering through other means but none thus far have been directed at the cold water extraction technique.Conclusions: Clinicians should be aware of the potential toxicity from tampered nonprescription analgesics. There is also the need for public health education regarding the potential risks associated with these methods.

Development of a linear dual column HPLC-MS/MS method and clinical genetic evaluation for tramadol and its phase I and II metabolites in oral fluid

Tramadol is a centrally acting synthetic opioid analgesic and has received special attention due to its abuse potential and unexpected responses induced by CYP2D6 polymorphism. Oral fluid is an advantageous biofluid for drug analysis due to non-invasive sampling and high correlation of drug concentrations with plasma. However, few studies have been performed on distribution of tramadol and its metabolites in oral fluid. In the present study, a linear dual column HPLC-MS/MS method was developed and fully validated for the simultaneous determination of tramadol and its phase I [O-desmethyltramadol (ODMT), N-desmethyltramadol (NDMT) and N,O-didesmethyltramadol (NODMT)] and II metabolites in oral fluid. Furthermore, the distribution of tramadol and its metabolites, in relation to CYP2D6 genetic variations, in oral fluid was investigated following a clinical study including 23 subjects with CYP2D6*wt/*wt, CYP2D6*10/*10 or CYP2D6*5/*5. The validation results of selectivity, matrix effect, linearity, precision and accuracy were satisfactory. Pharmacokinetic parameters, such as C_ss,max and AUC_0-τ of tramadol, NDMT and NODMT, in the CYP2D6*10/*10 group were significantly higher than those in the CYP2D6*wt/*wt group. Moreover, the ratios of ODMT/tramadol, NDMT/tramadol and NODMT/NDMT correlated well with the CYP2D6 genotypes. We demonstrated that oral fluid is a promising biofluid for pharmacokinetic evaluation in relation to genetic variations.

The Pharmacokinetics of Morphine and Codeine in Human Plasma and Urine after Oral Administration of Qiangli Pipa Syrup

Papaveris pericarpium, a natural source of morphine and codeine, is the principal active component in many antitussive traditional Chinese medicines. We herein report the first PK study of papaveris pericarpium in human plasma and urine following oral administration of single (15, 30, 60 mL) and multiple dose (15 mL) of Qiangli Pipa Syrup (MOR 0.1 mg/mL, COD 0.028 mg/mL) by monitoring morphine and codeine using a HPLC-MS/MS method. Their T_max and t_1/2 values are independent of dosages, while the AUC_0-t linearly increased with higher dosages, indicating linear PK characteristics. AUC_0-t increased obviously after multiple doses, indicating possible risk of accumulative toxicity. Urine studies suggested risks of positive opiate drug tests with a cutoff of 300 ng/mL, which lasted 6-14 h at different doses. These results provide important information for clinical safety, efficacy and rational drug use of Qiangli Pipa Syrup and also guide the related judicial expertise of its administration.

Urine and oral fluid drug testing in support of pain management

In recent years, the abuse of opioid drugs has resulted in greater prevalence of addiction, overdose, and deaths attributable to opioid abuse. The epidemic of opioid abuse has prompted professional and government agencies to issue practice guidelines for prescribing opioids to manage chronic pain. An important tool available to providers is the drug test for use in the initial assessment of patients for possible opioid therapy, subsequent monitoring of compliance, and documentation of suspected aberrant drug behaviors. This review discusses the issues that most affect the clinical utility of drug testing in chronic pain management with opioid therapy. It focuses on the two most commonly used specimen matrices in drug testing: urine and oral fluid. The advantages and disadvantages of urine and oral fluid in the entire testing process, from specimen collection and analytical methodologies to result interpretation are reviewed. The analytical sensitivity and specificity limitations of immunoassays used for testing are examined in detail to draw attention to how these shortcomings can affect result interpretation and influence clinical decision-making in pain management. The need for specific identification and quantitative measurement of the drugs and metabolites present to investigate suspected aberrant drug behavior or unexpected positive results is analyzed. Also presented are recent developments in optimization of test menus and testing strategies, such as the modification of the standard screen and reflexed-confirmation testing model by eliminating some of the initial immunoassay-based tests and proceeding directly to definitive testing by mass spectrometry assays.

Detection of Hydrocodone and Morphine as Metabolites in Oral Fluid by LC-MS/MS in Patients Prescribed Codeine

A retrospective analysis of oral fluid drug testing results using LC-MS/MS was performed to determine the prevalence rates in oral fluid for codeine (COD) and 3 COD metabolites-morphine (MOR), norhydrocodone (NHC), and hydrocodone (HCOD). Oral fluid samples were collected using Quantisal oral fluid collection device (Immunalysis Inc.) and submitted to Millennium Health, LLC for the routine drug analysis by LC-MS/MS. Consistent with previously published literature, COD was the primary analyte detected in oral fluid after the use of COD. In COD-positive samples, HCOD, MOR, and NHC were detected at rates of 68.4%, 18.4%, and 6.3%, respectively. Concentration ranges of these analytes were 1.0 to >2000 ng/mL for COD, 1.0-20.2 ng/mL for MOR, 1.0-740.0 ng/mL for HCOD, and 2.1-47.5 ng/mL for NHC. In contrast to urine, where HCOD is typically detected as a minor metabolite of COD, HCOD was the most commonly detected metabolite in oral fluid in samples testing positive for COD with reported prescriptions for COD. This observation suggests that care should be taken when interpreting HCOD positives in oral fluid results, and that the use of COD should be considered as one possible explanation for HCOD positives.

The Abuse Potential of Prescription Opioids in Humans-Closing in on the First Century of Research

While opioids are very effective analgesics for treating acute pain, humans have struggled with opiate addiction for millenia. An opium abuse epidemic in the early 1900's led the US government to develop a systematic research infrastructure and scientific plan to produce new compounds with analgesic properties but without abuse liability. This review describes the techniques that were developed for testing in the human laboratory, including empirically derived outcome measures and required elements for human abuse potential assessment. The evaluation and characterization of semi-synthetic and synthetic opioids, including full mu opioid agonists, partial agonists and mixed agonist-antagonists, are described across several decades of research. Finally, the prescription opioid epidemic beginning in the 1990's in the US led to a resurgence in abuse potential evaluations, and the application of these methods to the study of novel abuse-deterrent formulations is discussed.

Opioid Concentrations in Oral Fluid and Plasma in Cancer Patients With Pain

CONTEXT

Measuring opioid concentrations in pain treatment is warranted in situations where optimal opioid analgesia is difficult to reach.

OBJECTIVES

To assess the usefulness of oral fluid (OFL) as an alternative to plasma in opioid concentration monitoring in cancer patients on chronic opioid therapy.

METHODS

We collected OFL and plasma samples from 64 cancer patients on controlled-release (CR) oral morphine, CR oral oxycodone, or transdermal (TD) fentanyl for pain. Samples were obtained on up to five separate days.

RESULTS

A total of 213 OFL and plasma samples were evaluable. All patients had detectable amounts of the CR or TD opioid in both plasma and OFL samples. The plasma concentrations of oxycodone and fentanyl (determination coefficient R(2) = 0.628 and 0.700, respectively), but not morphine (R(2) = 0.292), were moderately well correlated to the daily opioid doses. In contrast to morphine and fentanyl (mean OFL/plasma ratio 2.0 and 3.0, respectively), the OFL oxycodone concentrations were significantly higher than the respective plasma concentrations (mean OFL/plasma ratio 14.9). An active transporter could explain the much higher OFL vs. plasma concentrations of oxycodone compared with morphine and fentanyl.

CONCLUSION

OFL analysis is well suited for detecting the studied opioids. For morphine and fentanyl, an approximation of the plasma opioid concentrations is obtainable, whereas for oxycodone, the OFL/plasma concentration relationship is too variable for reliable approximation results.

Effects of three therapeutic doses of codeine/paracetamol on driving performance, a psychomotor vigilance test, and subjective feelings

RATIONALE

Some recent pharmacoepidemiological studies revealed an elevated risk of driving accidents after opioid analgesics uses. Among analgesics, codeine is often associated with paracetamol in numerous pharmaceutical specialties.

OBJECTIVES

The objective of this study was to evaluate the dose-effect relationship of three usual therapeutic doses of codeine/paracetamol on driving ability, psychomotor performance, subjective alertness, in link with blood concentrations in healthy young volunteers.

METHODS

Driving performance, responses to psychomotor vigilance tests, and scales reflecting alertness were evaluated during the morning after drug intake in a double-blind, randomized, placebo-controlled study. Sixteen healthy volunteers (23.4 ± 2.7 years old, 8 men and 8 women) participated in this balanced, cross-over study. Three doses of codeine/paracetamol (20/400, 40/800, 60/1200 mg) were evaluated against placebo. Two blood samples were collected, 1 and 4 h after drug intake. In serum, codeine and morphine concentrations were determined in serum using high-performance liquid chromatography electrospray ionization-tandem mass spectrometry, and paracetamol concentrations using fluorescence polarization immunoassay.

RESULTS

Driving and psychomotor performance were not affected by any of the three codeine/paracetamol doses. However, significant, though modest, correlations were observed between the driving parameters and both morphine and codeine blood concentrations.

CONCLUSIONS

This study did not reveal any significant impairment in performance due to the three therapeutic doses used in healthy young volunteers. However, the relationships between drug blood concentration and behavioral measures suggest that an inter-subject variability in blood concentration may influence the power of the observed drug effect.

Abuse liability and reinforcing efficacy of oral tramadol in humans

BACKGROUND

Tramadol, a monoaminergic reuptake inhibitor, is hepatically metabolized to an opioid agonist (M1). This atypical analgesic is generally considered to have limited abuse liability. Recent reports of its abuse have increased in the U.S., leading to more stringent regulation in some states, but not nationally. The purpose of this study was to examine the relative abuse liability and reinforcing efficacy of tramadol in comparison to a high (oxycodone) and low efficacy (codeine) opioid agonist.

METHODS

Nine healthy, non-dependent prescription opioid abusers (6 male and 3 female) participated in this within-subject, randomized, double blind, placebo-controlled study. Participants completed 14 paired sessions (7 sample and 7 self-administration). During each sample session, an oral dose of tramadol (200 and 400 mg), oxycodone (20 and 40 mg), codeine (100 and 200 mg) or placebo was administered, and a full array of abuse liability measures was collected. During self-administration sessions, volunteers were given the opportunity to work (via progressive ratio) for the sample dose or money.

RESULTS

All active doses were self-administered; placebo engendered no responding. The high doses of tramadol and oxycodone were readily self-administered (70%, 59% of available drug, respectively); lower doses and both codeine doses maintained intermediate levels of drug taking. All three drugs dose-dependently increased measures indicative of abuse liability, relative to placebo; however, the magnitude and time course of these and other pharmacodynamic effects varied qualitatively across drugs.

CONCLUSIONS

This study demonstrates that, like other mu opioids, higher doses of tramadol function as reinforcers in opioid abusers, providing new empirical data for regulatory evaluation.

Methadone, codeine and acute haemorrhagic necrotising pancreatitis: which came first?

Acute haemorrhagic necrotising pancreatitis lead to the death at home of a young female who was on a methadone maintenance programme. Toxic levels of codeine with potentially lethal levels of methadone and morphine were found at post-mortem. Whether opiates caused the pancreatitis or were the consequence of self-medication for pain is impossible to differentiate. Forensic toxicology may pose the question but be unable to provide the answer.

Drivers under the influence of drugs of abuse: quantification of cocaine and impaired driving

In recent years, the interest in oral fluid as a biological matrix has significantly increased, particularly for detecting driving under the influence of drugs. In this study, the concentration of cocaine and its relationship with clinical symptoms in drivers suspected of driving under the influence of drugs was evaluated. A total of 154 samples of oral fluid, which tested positive for cocaine in previous immunoassay screening, Cozart Drug Detector System, were confirmed using gas chromatography/mass spectrometry method. In Catalonia, during 2007-2010, there were 1791 samples positive for cocaine among a total of 3468 samples taken from drivers who tested positive for any drug of abuse. The evaluation of clinical symptoms was through a questionnaire that was filled in by the police officers who collected the samples. The mean concentration of cocaine was 4.11 mg/l and median concentration was 0.38 mg/l (range 0.01-345.64 mg/l). Clinical impairment symptoms such as motor coordination, walking, speech, mood and state of pupils were not significant. The testing of oral fluids presents fewer ethical problems than blood or urine.

Screening for drugs of abuse: which matrix, oral fluid or urine?

Urine is recognized as the prime matrix for drug test screening with well-established methods and testing protocols. Its major limitation is with regard to the inconvenience of sample collection and lack of integrity due to adulteration, dilution, drug spiking or sample exchange. The question is whether oral fluid, with its apparent better sample integrity, can replace urine for drug screening. This review examines the sample integrity problems and the advantages and limitations of oral fluid and urine in drug screening programmes. The variety of sample collection devices for oral fluid is shown to be a problem with recovery and detection for some drugs. This is examined in relation to the pharmacokinetics of drug metabolism and excretion in this matrix. Buccal contamination with drugs in oral fluid may also cause problems with interpretation. The clinical advantages of oral fluid analysis compared with urine testing are highlighted. Parent drugs are often found in oral fluid where only their metabolites may be found in urine, for example the benzodiazepines. 6-Monoacetylmorphine, an indicative marker of heroin, has a high prevalence in oral fluid from users of this drug but its detection in urine is limited due to its short half-life. Advances in analytical techniques, particularly chromatography linked to tandem mass spectrometry, are helping to promote oral fluid analysis. However, the lack of concordance studies examining both urine and oral fluid drug levels and kinetics in the clinical setting is of some concern.

Cannabinoids and metabolites in expectorated oral fluid after 8 days of controlled around-the-clock oral THC administration

Oral fluid (OF) is an increasingly accepted matrix for drug testing programs, but questions remain about its usefulness for monitoring cannabinoids. Expectorated OF specimens (n = 360) were obtained from 10 adult daily cannabis smokers before, during, and after 37 20-mg oral Δ(9)-tetrahydrocannabinol (THC) doses over 9 days to characterize cannabinoid disposition in this matrix. Specimens were extracted and analyzed by gas chromatography-mass spectrometry with electron-impact ionization for THC, 11-hydroxy-THC, cannabidiol, and cannabinol, and negative chemical ionization for 11-nor-9-carboxy-THC (THCCOOH). Linear ranges for THC, 11-hydroxy-THC, and cannabidiol were 0.25-50 ng/mL; cannabinol 1-50 ng/mL; and THCCOOH 5-500 pg/mL. THCCOOH was the most prevalent analyte in 344 specimens (96.9%), with concentrations up to 1,390.3 pg/mL. 11-hydroxy-THC, cannabidiol, and cannabinol were detected in 1, 1, and 3 specimens, respectively. THC was detected in only 13.8% of specimens. The highest THC concentrations were obtained at admission (median 1.4 ng/mL, range 0.3-113.6) from previously self-administered smoked cannabis. A total of 2.5 and 3.7% of specimens were THC-positive at the recommended Substance Abuse and Mental Health Services Administration (2 ng/mL) and Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) (1 ng/mL) confirmation cutoffs, respectively. THC is currently the only analyte for monitoring cannabis exposure in OF; however, these data indicate chronic therapeutic oral THC administration and illicit oral THC use are unlikely to be identified with current guidelines. Measurement of THCCOOH may improve the detection and interpretation of OF cannabinoid tests and minimize the possibility of OF contamination from passive inhalation of cannabis smoke.

Bioanalytical procedures and recent developments in the determination of opiates/opioids in human biological samples

The use and abuse of illegal drugs affects all modern societies, and therefore the assessment of drug exposure is an important task that needs to be accomplished. For this reason, the reliable determination of these drugs and their metabolites in biological specimens is an issue of utmost relevance for both clinical and forensic toxicology laboratories in their fields of expertise, including in utero drug exposure, driving under the influence of drugs and drug use in workplace scenarios. Most of the confirmatory analyses for abused drugs in biological samples are performed by gas chromatographic-mass spectrometric methods, but use of the more recent and sensitive liquid chromatography-(tandem) mass spectrometry technology is increasing dramatically. This article reviews recently published articles that describe procedures for the detection of opiates in the most commonly used human biological matrices, blood and urine, and also in unconventional ones, e.g. oral fluid, hair, and meconium. Special attention will be paid to sample preparation and chromatographic analysis.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Pharmacokinetics of cocaine and metabolites in human oral fluid and correlation with plasma concentrations after controlled administration

Oral fluid is an attractive alternative matrix for drug testing with a noninvasive and directly observed collection, but there are few controlled cocaine administration studies to guide interpretation.

MATERIALS AND METHODS

While residing on a closed research unit for up to 10 weeks under constant medical supervision, 19 participants were administered 75 mg/70 kg subcutaneous cocaine and 14 received 150 mg/70 kg. The disposition of cocaine, benzoylecgonine (BE), and ecgonine methyl ester (EME) into oral fluid was determined by gas chromatography-mass spectrometry for 0.08 to 48 hours after administration.

RESULTS

In oral fluid collected by citric acid candy-stimulated expectoration, cocaine first appeared in oral fluid 0.08 to 0.32 hours after dosing and was rapidly eliminated with half-lives of 1.1 to 3.8 hours. BE and EME were first detected 0.08 to 1.0 hours after dosing with longer half-lives of 3.4 to 13.8 (BE) and 2.4 to 15.5 hours (EME) (P < 0.05). Oral fluid and plasma concentrations were significantly correlated for cocaine, BE, and EME (P < 0.0001). There were no significant differences (P > 0.05) in first and last detection times with the 8-μg/L cutoff proposed by the Substance Abuse and Mental Health Services Administration or the 10-μg/L cutoff from the European initiative, Driving Under the Influence of Drugs, Alcohol and Medicines. Metabolite:cocaine ratios increased after cocaine administration, potentially helpful for interpreting time of last use. Comparison of oral fluid collection through citric acid candy-stimulated expectoration, citric acid-treated Salivette, and neutral cotton Salivette devices did not reveal significant differences between devices for areas under the curve for cocaine, BE, or EME (P > 0.05).

DISCUSSION AND CONCLUSION

These results provide additional evidence for interpreting cocaine and metabolite concentrations in oral fluid and oral fluid's usefulness as an alternative matrix for drug testing.

Uptake of codeine into intestinal epithelial (Caco-2) and brain endothelial (RBE4) cells

Orally administered codeine has to permeate both the intestinal and the blood-brain barrier in order to act as analgesic and cough suppressant. In this study we characterized the uptake of codeine at intestinal epithelial (Caco-2) and brain endothelial (RBE4) cells. At both cell types, uptake of [(3)H]codeine was independent of an inwardly directed Na(+) gradient. Uptake was, however, strongly stimulated by an outwardly directed H(+) gradient and inhibited by the protonophore FCCP. [(3)H]Codeine uptake into Caco-2 cells was strongly temperature dependent. In the presence of excess amounts of unlabeled codeine, the uptake was inhibited by up to 87% (Caco-2) or 94% (RBE4), respectively. Synthetic opioids and some non-opioid organic cations like propranolol, pyrilamine and quinidine potently inhibited [(3)H]codeine uptake. Several prototype substrates of known transporters for amino acids, neurotransmitters and organic cations were ineffective. Our data are consistent with a hypothetic saturable, H(+)-dependent (antiport) mechanism not yet identified on a molecular level. The pH dependence of codeine uptake and its intracellular accumulation can partially also be explained by a model comprising diffusional membrane permeation of unionized species of codeine followed by codeine sequestration into acidic vesicles and distribution into cellular lipids.

Oral fluid testing for drugs of abuse

BACKGROUND

Oral fluid (OF) is an exciting alternative matrix for monitoring drugs of abuse in workplace, clinical toxicology, criminal justice, and driving under the influence of drugs (DUID) programs. During the last 5 years, scientific and technological advances in OF collection, point-of-collection testing devices, and screening and confirmation methods were achieved. Guidelines were proposed for workplace OF testing by the Substance Abuse and Mental Health Services Administration, DUID testing by the European Union's Driving under the Influence of Drugs, Alcohol and Medicines (DRUID) program, and standardization of DUID research. Although OF testing is now commonplace in many monitoring programs, the greatest current limitation is the scarcity of controlled drug administration studies available to guide interpretation.

CONTENT

This review outlines OF testing advantages and limitations, and the progress in OF that has occurred during the last 5 years in collection, screening, confirmation, and interpretation of cannabinoids, opioids, amphetamines, cocaine, and benzodiazepines. We examine controlled drug administration studies, immunoassay and chromatographic methods, collection devices, point-of-collection testing device performance, and recent applications of OF testing.

SUMMARY

Substance Abuse and Mental Health Services Administration approval of OF testing was delayed because questions about drug OF disposition were not yet resolved, and collection device performance and testing assays required improvement. Here, we document the many advances achieved in the use of OF. Additional research is needed to identify new biomarkers, determine drug detection windows, characterize OF adulteration techniques, and evaluate analyte stability. Nevertheless, there is no doubt that OF offers multiple advantages as an alternative matrix for drug monitoring and has an important role in DUID, treatment, workplace, and criminal justice programs.

Current technologies and considerations for drug bioanalysis in oral fluid

Drug oral fluid analysis was first used almost 30 years ago for the purpose of therapeutic drug monitoring. Since then, oral fluid bioanalysis has become more popular, mainly in the fields of pharmacokinetics, workplace drug testing, criminal justice, driving under the influence testing and therapeutic drug monitoring. In fact, oral fluid can provide a readily available and noninvasive medium, without any privacy loss by the examinee, which occurs, for instance, during the collection of urine samples. It is believed that drug concentrations in oral fluid may parallel those measured in blood. This feature makes oral fluid an alternative analytical specimen to blood, which assumes particular importance in roadside testing, the most published application of this sample. Great improvements in the development of accurate and reliable methods for sample collection, in situ detection devices (on-site drug detection kits), and highly sensitive and specific analytical methods for oral fluid testing of drugs have been observed in the last few years. However, without mass spectrometry-based analytical methods, such as liquid chromatography coupled to mass spectrometry (LC–MS) or tandem mass spectrometry (LC–MS/MS), the desired sensitivity would not be met, due to the low amounts of sample usually available for analysis. This review will discuss a series of published papers on the applicability of oral fluid in the field of analytical, clinical and forensic toxicology, with a special focus on its advantages and drawbacks over the normally used biological specimens and the main technological advances over the last decade, which have made oral fluid analysis of drugs possible.

Roadside oral fluid testing: Comparison of the results of Drugwipe 5 and Drugwipe Benzodiazepines on-site tests with laboratory confirmation results of oral fluid and whole blood

Drugged drivers pose a serious threat to other people in traffic as well as to themselves. Reliable oral fluid screening devices for on-site screening of drugged drivers would be both a useful and convenient means for traffic control. In this study we evaluated the appropriateness of Drugwipe 5 and Drugwipe Benzodiazepines oral fluid on-site tests for roadside drug screening. Drivers suspected of driving under the influence of drugs were screened with the Drugwipe tests. Oral fluid and whole blood samples were collected from the drivers and tested for amphetamine-type stimulant drugs, cannabis, opiates, cocaine and benzodiazepines by immunological methods, GC and GC-MS. The performance evaluations of the tests were made by comparing the results of the Drugwipe tests with laboratory GC-MS confirmation results of oral fluid or whole blood. In addition to the performance evaluations of the Drugwipe tests based on laboratory results, a questionnaire on the practical aspects of the tests was written for the police officers who performed the tests. The aim of the questionnaire was to obtain user comments on the practicality of the tests as well as the advantages and weak points of the tests. The results of the performance evaluations were: for oral fluid (sensitivity; specificity; accuracy) amphetamines (95.5%; 92.9%; 95.3%), cannabis (52.2%; 91.2%; 85.1%), cocaine (50.0%; 99.3%; 98.6%), opiates (100%; 95.8%; 95.9%), benzodiazepines (74.4%; 84.2%; 79.2%) and for whole blood accordingly, amphetamines (97.7%; 86.7%; 95.9%), cannabis (68.3%; 87.9%; 84.9%), cocaine (50.0%; 98.5%; 97.7%), opiates (87.5%; 96.9%; 96.6%) and benzodiazepines (66.7%; 87.0%; 74.4%). Although the Drugwipe 5 successfully detected amphetamine-type stimulant drugs and the police officers were quite pleased with the current features of the Drugwipe tests, improvements must still be made regarding the detection of cannabis and benzodiazepines.

Simultaneous quantification of 11 pivotal metabolites in neural tube defects by HPLC-electrospray tandem mass spectrometry

One-carbon metabolism that involves folate metabolism and homocysteine metabolism plays a powerful role in embryonic development. Any impairment to this metabolism during the neurulation process would trigger the occurrence of neural tube defects (NTDs). The great importance of one-carbon metabolism necessitates the establishment of methodology to determine the relative compounds involved in the metabolic cycles. We have developed a sensitive method for measurement of 11 pivotal compounds by using high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS/MS) in sera of pregnant women. Use of an aqueous chromatography column increased retention time and separation of the polar compounds in the system, resulting in fewer co-elution and interference from the other compounds that can lead to ion suppression. Calibration curves suitable for the analysis of maternal serum were linear (r(2)>0.997) with limits of detection from 0.05 to 1ng/mL. Intra-day coefficients of variation (CVs) and inter-day CVs were both lower than 11%. With the developed method, 96 serum samples including 46 cases and 50 controls were analyzed. The established method provided a reliable method for quantifying most of the compounds involved in the one-carbon metabolism simultaneously, thus made it possible to elucidate NTDs with multiple factors instead of one single and provided a solid foundation for the diagnosis and prevention of NTDs as well as some other one-carbon metabolism related diseases.

Bioanalytical procedures for determination of drugs of abuse in oral fluid

Recent advances in analytical techniques have enabled the detection of drugs and drug metabolites in oral fluid specimens. Although GC-MS is still commonly used in practice, many laboratories have developed and successfully validated methods for LC-MS(-MS) that can detect a large number of compounds in the limited sample volume available. In addition, several enzyme immunoassays have been commercialized for the detection of drugs of abuse in oral fluid samples, enabling the fast screening and selection of presumably positive samples. A number of concerns are discussed, such as the variability in the volume of sample collected and its implications in terms of quantitative measurements, and the drug recoveries of the many different specimen collection systems on the market. Additional considerations that also receive attention are the importance of providing complete validation data with respect to analyte stability, matrix effect, and the choice of collection method.

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.

Interpretation of oral fluid tests for drugs of abuse

Oral fluid testing for drugs of abuse offers significant advantages over urine as a test matrix. Collection can be performed under direct observation with reduced risk of adulteration and substitution. Drugs generally appear in oral fluid by passive diffusion from blood, but also may be deposited in the oral cavity during oral, smoked, and intranasal administration. Drug metabolites also can be detected in oral fluid. Unlike urine testing, there may be a close correspondence between drug and metabolite concentrations in oral fluid and in blood. Interpretation of oral fluid results for drugs of abuse should be an iterative process whereby one considers the test results in the context of program requirements and a broad scientific knowledge of the many factors involved in determining test outcome. This review delineates many of the chemical and metabolic processes involved in the disposition of drugs and metabolites in oral fluid that are important to the appropriate interpretation of oral fluid tests. Chemical, metabolic, kinetic, and analytic parameters are summarized for selected drugs of abuse, and general guidelines are offered for understanding the significance of oral fluid tests.