Validation of new methods

Reliable analytical data are a prerequisite for correct interpretation of toxicological findings in the evaluation of scientific studies, as well as in daily routine work. Unreliable analytical data might not only be contested in court, but could also lead to unjustified legal consequences for the defendant or to wrong treatment of the patient. Therefore, new analytical methods to be used in forensic and/or clinical toxicology require careful method development and thorough validation of the final method. This is especially true in the context of quality management and accreditation, which have become matters of increasing relevance in analytical toxicology in recent years. In this paper, important considerations in analytical method validation will be discussed which may be used as guidance by scientists wishing to develop and validate analytical methods.     

Postmortem toxicology of drugs of abuse

Conducting toxicology on post-mortem specimens provides a number of very significant challenges to the scientist. The range of additional specimens include tissues such as decomposing blood and other tissues, hair, muscle, fat, lung, and even larvae feeding on the host require special techniques to isolate a foreign substance and allow detection without interference from the matrix. A number of drugs of abuse are unstable in the post-mortem environment that requires careful consideration when trying to interpret their significance. Heroin, morphine glucuronides, cocaine and the benzodiazepines are particularly prone to degradation. Moreover, redistributive process can significantly alter the concentration of drugs, particularly those with a higher tissue concentration than the surrounding blood. The designer amphetamines, methadone and other potent opioids will increase their concentration in blood post-mortem. These processes together with the development of tolerance means that no concentration of a drug of abuse can be interpreted in isolation without a thorough examination of the relevant circumstances and after the conduct of a post-mortem to eliminate or corroborate relevant factors that could impact on the drug concentration and the possible effect of a substance on the body. This article reviews particular toxicological issues associated with the more common drugs of abuse such as the amphetamines, cannabinoids, cocaine, opioids and the benzodiazepines.     

A fatality due to propofol poisoning.

This report describes a suicide by self-administration of propofol in a 29-year-old female radiographer. This is the first published report of death by overdosage with propofol. Propofol was detected in tissues using high performance liquid chromatography. Post mortem femoral blood and liver concentrations of propofol were 0.22 mg/L and 1.4 mg/kg, respectively. The scene suggested that a dose of 400 mg was used.     

Review: Pharmacokinetics of illicit drugs in oral fluid

This article reviews studies that have measured drug concentrations in oral fluid following controlled dosing regimens. A total of 23 studies have been identified over the last 15 years. These show that the amphetamines including designer amphetamines, cocaine, cannabis and cocaine are quickly found in oral fluid following dosing and usually have similar time-courses to that in plasma. Following common doses peak oral fluid concentrations exceed 0.1 μg/mL and often even 1 μg/mL. The drug concentration will depend on whether a dilution step occurs with buffer as part of the sampling procedure. The uses of collectors that stimulate oral fluid usually reduce the drug concentration compared to a non-stimulated manner. This reduction will not disadvantage the recipient since it will potentially reduce the detectablity of drug in oral fluid compared to non-stimulated collections. Only one recent study has been reported for a benzodiazepine. This showed nanogram per milliliter concentrations for flunitrazepam. More studies are required for benzodiazepines and indeed for other drugs, particularly in multiple drug situations and where disease may affect the pharmacokinetics of drugs.     

Drugs in oral fluid in randomly selected drivers

There were 13,176 roadside drug tests performed in the first year of the random drug-testing program conducted in the state of Victoria. Drugs targeted in the testing were methamphetamines and Δ⁹-tetrahydrocannabinol (THC). On-site screening was conducted by the police using DrugWipe^®, while the driver was still in the vehicle and if positive, a second test on collected oral fluid, using the Rapiscan^®, was performed in a specially outfitted “drug bus” located adjacent to the testing area. Oral fluid on presumptive positive cases was sent to the laboratory for confirmation with limits of quantification of 5, 5, and 2 ng/mL for methamphetamine (MA), methylenedioxy-methamphetamine (MDMA), and THC, respectively. Recovery experiments conducted in the laboratory showed quantitative recovery of analytes from the collector. When oral fluid could not be collected, blood was taken from the driver and sent to the laboratory for confirmation. These roadside tests gave 313 positive cases following GC–MS confirmation. These comprised 269, 118, and 87 cases positive to MA, MDMA, and THC, respectively. The median oral concentrations (undiluted) of MA, MDMA, and THC was 1136, 2724, and 81 ng/mL. The overall drug positive rate was 2.4% of the screened population. This rate was highest in drivers of cars (2.8%). The average age of drivers detected with a positive drug reading was 28 years. Large vehicle (trucks over 4.5 t) drivers were older; on average at 38 years. Females accounted for 19% of all positives, although none of the positive truck drivers were female. There was one false positive to cannabis when the results of both on-site devices were considered and four to methamphetamines.     

Age estimation using CT imaging of the third molar tooth, the medial clavicular epiphysis, and the spheno-occipital synchondrosis: a multifactorial approach

A multi-factorial method for estimating age was devised based on the development of the 3rd molar tooth, the medial clavicular epiphysis, and the spheno-occipital synchondrosis, using multiple regression as the means to construct age estimation formulae and CT scanning as the imaging modality. The sample consisted of approximately 600 individuals from a contemporary Australian population, between the ages of 15 and 25 years, who were admitted to the Victorian Institute of Forensic Medicine, Melbourne, Australia, for the purposes of medico-legal death investigation. Results show that the spheno-occipital synchondrosis does not contribute to the age estimation model for this age cohort. The regression computation for the 3rd molar tooth and medial clavicle, when combined into a single multiple regression calculation, provides a robust model with tighter age ranges at the 95% confidence interval (CI) than when each age marker is used individually. This research provides a method to estimate age for unknown age Australian individuals in the problematic age group of 15-25 years with greater precision than previously possible.     

Assessment of the stability of 30 antipsychotic drugs in stored blood specimens

The accuracy of antemortem diagnosis of pulmonary embolism is within the range of just 10-30%, so representing one of the most frequent missed diagnosis in sudden, unexpected death. We describe 43 fatal cases of pulmonary embolism as confirmed by post-mortem examination. The aim of our study was to verify the systematic search for the most common genetic thrombophilias (Factor V Leiden (G1691A) and FII (G20210A) gene variants) and dating the thrombus. As a whole, 41 patients (95.3%) had at least one risk factor. Pre-existing symptoms are described just before fatal embolism in 18 (41.9%) out 43 patients. In 18 out of 43 (41.9%) it was not possible to find the thrombotic site. In 24 out of the remaining 25 cases the involvement of the deep veins of one leg was shown; in 1 case the thrombus was localised in the inferior caval vein. 10 (41.7%) were iliac vein thromboses, 7 (29.1%) femoral, 2 (8.3%) popliteal, 3 (12.6%) posterior-tibial, 1 (4.1%) anterior-tibial and 1 (4.1%) peroneal vein thromboses. In our cohort of patients, 4 (10%) out of 40 cases carried the 20210A prothrombin gene variant in heterozygosis. One (2.5%) out of 40 carried the Factor V Leiden (G1691A) gene variant in heterozygosis. Patients carrying these gene variants in homozygosis or carrying both were not present in our case-series. We strongly underline the relevance of a complete methodological approach, integrating clinical data by means of autopsy findings and histological study. On the contrary, investigating common inherited thrombophilia is not warranted.     

Serotonin toxicity involving MDMA (ecstasy) and moclobemide

The use of MDMA (ecstasy) in Australia is a widespread and growing problem, promoting acute toxicity and disease which can lead to premature death in users. We report four cases of fatal serotonin toxicity caused by the combination of MDMA and moclobemide, a reversible MAO-A inhibitor with potent serotonergic activity. Despite the highly reported toxicity of this drug combination, there are very few reports of fatalities attributed to a MDMA and moclobemide interaction. Pathology and toxicology reports, initial police reports and coroners' findings were examined to determine the circumstances of the deaths. Symptoms of some of the four cases as reported by paramedics and medical staff included hyperthermia, hyperkalemia, profuse sweating, twitching and shaking. Two cases involved moclobemide concentrations consistent with common prescribed doses, while the other two cases involved much higher concentrations often associated with toxicity. Three of these cases presented with some form of heart disease.     

Postmortem stability and interpretation of beta 2-agonist concentrations.

This paper describes a series of stability and redistribution studies aimed at understanding the presence and significance of beta 2-agonists in asthma deaths. Salbutamol and terbutaline were shown to be stable in postmortem blood at 23 degrees C for 1 week, 4 degrees C for 6 months and -20 degrees C for 1 to 2 years. However, fenoterol was shown to degrade at 23 degrees C (83% loss), 4 degrees C (93% loss) and -20 degrees C (66% loss) over the same time. Salbutamol concentrations detected in blood taken at the time of body admission to the mortuary were not significantly different from the concentrations detected in blood taken from the same cases at the time of autopsy (45 h later). This suggests that significant postmortem redistribution of salbutamol is unlikely to occur during this period. Postmortem blood concentrations of at least salbutamol are likely to reflect the concentration of these drugs in the body at the time of death.     

Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC x GC-TOFMS) for drug screening and confirmation

Comprehensive two-dimensional gas chromatography (GC x GC) is applied to analysis of drug standard mixtures containing 78 drugs of interest in forensic samples. For this study, underivatised drugs were employed. While several of the drugs were not detected at the low concentrations employed in the samples, most could be satisfactorily assigned their first and second dimension retentions in the GC x GC retention plane. For this study, time-of-flight mass spectrometry (TOFMS) detection was used. The enhanced separation possible in GC x GC is demonstrated, and typical linearity and apparatus precision are shown for tramadol, diazepam, olanzapine and desipramine using selected qualifier ions. Mass spectral library search quality for the detection of drugs in a selection of authentic forensic cases, along with retention position in the 2D retention plane, is used to support positive identification of the presence of the drugs. The analysis of 'difficult' drugs paracetamol and phenytoin is shown to produce anomalous chromatographic peak shape in the 2D plane, whereas most drugs gave acceptable peak shapes. The GC x GC technique was applied to screening drugs in forensic samples, with either flame ionisation (FID) or TOFMS detection, and compared favourably with conventional single column GC-MS analysis when tested for diazepam in an authentic forensic study.