Validation of Conversion Factors for Therapeutic Drug Monitoring of Lacosamide, Lamotrigine, and Levetiracetam in Dried Capillary Blood.

BACKGROUND: Estimation of serum concentrations of antiseizure medications (ASMs) based on dried capillary blood is an alternative method for therapeutic drug monitoring of epilepsy. The aim of this study was to validate the conversion factors for lacosamide (LCM), lamotrigine (LTG), and levetiracetam (LEV), which were determined in an independent patient sample in a previous study, and identify the most accurate conversion method (simple ratio and regression). METHODS: Venous and capillary blood samples were collected from adult inpatients with epilepsy treated with LCM (n = 25), LTG (n = 27), and/or LEV (n = 29) before the morning dose (T1) and approximately 2 hours after (T2). Capillary blood was collected using volumetric absorptive microsampling, and the ASM concentrations were measured using a validated liquid chromatography-mass spectrometry method for dried blood samples. Serum concentrations were estimated using conversion factors and compared with those measured using routine laboratory methods. RESULTS: For all 3 ASMs, the simple ratio approach performed better than the regression approach. Intraclass correlation coefficients revealed a high agreement between the estimated and measured serum concentrations (LCM T1: 0.93, T2: 0.90; LTG T1: 0.91, T2: 0.91; and LEV T1: 0.97, T2: 0.94). The criteria of the European Medicines Agency for cross-validation were fulfilled for LCM (T1: 72%; T2: 75%) and LEV (T1: 86%; T2: 75%), whereas for LTG, this was only true for capillary blood concentrations ≤11 µ g/mL [42.9 µ mol/L; T1: 72% (vs. 63% for total range), T2: 67% (vs. 62%)]. CONCLUSIONS: Estimating serum concentrations using capillary blood concentrations is feasible and accurate for LCM and LEV over a wide concentration range, as found in clinical practice. The applicability of this mehod for LTG is limited by its greater variability at higher concentrations; however, acceptable results were achieved for the large proportion of patients with low and medium LTG concentrations.

Therapeutic Drug Monitoring of Lamotrigine, Lacosamide, and Levetiracetam in Dried Capillary Blood-Determination of Conversion Factors for Serum-Based Reference Ranges.

BACKGROUND: Drug concentrations of antiepileptic drugs (AEDs) are routinely determined from blood serum or plasma at trough levels (before intake of morning dose). In capillary blood collection, blood is taken from the fingertip with the aid of a disposable tool and dried on absorbent material. The volumetric absorptive microsampling technique offers several advantages over the use of filter paper cards. The aim of this study was to determine conversion factors for the estimation of AED serum concentrations from capillary blood concentrations. METHODS: Venous and capillary blood samples were collected from adult inpatients with epilepsy who were treated with lacosamide (LCM, n = 30), lamotrigine (LTG, n = 40), and/or levetiracetam (LEV, n = 36). A validated liquid chromatography-mass spectrometry (LC-MS) method for dried blood samples for these AEDs was compared with routine serum laboratory methods. Method agreement was evaluated using different regression techniques, and the conversion factors were calculated. RESULTS: Regression analyses revealed a linear relationship between serum and capillary blood concentrations for all 3 AEDs (r ≥ 0.95). For LTG, the regression intercept was significantly different from 0, indicating that the relationship was linear, but not necessarily proportional. Although LEV and LCM concentrations tended to be lower in capillary blood than in serum (mean ratio of serum concentration to capillary blood concentration: 1.14 and 1.22, respectively), LTG concentrations were higher in capillary blood (mean ratio = 0.85). CONCLUSIONS: The estimation of serum concentrations from measured capillary blood concentrations is feasible for LCM, LTG, and LEV. A simple ratio approach using the mean ratio and Passing-Bablok regression showed the best results for all 3 AEDs. The volumetric absorptive microsampling technique facilitates the quantitative sample collection of capillary blood and overcomes the drawbacks associated with the classical dried blood spot technique.

Development and validation of an LC-MS/MS method for relevant drugs in epilepsy patients using dried blood spots.

Epilepsy is one of the most common diseases of the central nervous system globally. To ensure the correct dosage of antiepileptic treatment, it is helpful to check the blood levels of the administered substances regularly. The analysis of the capillary dried blood samples provides a promising and less-invasive alternative to venous blood collection. Therefore, the aim of the present study was to develop an LC-MS method for the quantification of 22 commonly used drugs in patients with an epileptic syndrome and 5 drug metabolites in one dried blood spot (DBS). The calibration ranges were selected in such a way that the therapeutic reference ranges in serum for the respective substances were completely covered. The analytical validation was successfully performed according to relevant guidelines with a consideration of requirements for DBS analysis. Proof of concept of the developed method was obtained by the analysis of DBSs from 282 authentic leftover ethylenediaminetetraacetic acid blood samples, which were compared with the corresponding serum concentrations. Altogether, the results show a dependency on the blood/plasma (b/p) ratios of the respective analytes so that for drugs with b/p ratios close to one, for example, lacosamide, levetiracetam, brivaracetam, and sertraline, a good accordance was observed.

Is urine an alternative to cosmetically treated hair for the detection of drugs and alcohol?

This study attempts to assess the utility of the urine matrix as an alternative to cosmetically treated hair for the detection of drugs and alcohol for driving licence re-granting in 1026 cosmetically treated hair samples and 33 262 urine routine samples. No significant difference was observed between the percentage positive samples in cosmetically treated hair to those in urine at both the 95% and 99% significance level for amphetamines, cocaine, opiates, benzodiazepines, and methadone. Significant difference was found between the positivity rates of cannabinoids in cosmetically treated hair and that in urine indicating urine to be a better alternative to the use of the hair matrix even when cosmetically treated. The opposite was observed for the alcohol consumption marker ethyl glucuronide (EtG) for which the positivity rate in cosmetically treated hair was twice that in urine samples. Particularly for alcohol abstinence monitoring, as for the rehabilitative driving licence re-granting medical and psychological assessment (MPA) programme in Germany, it seems that ethyl glucuronide (EtG) in hair presents a much better alternative than urine testing, even when cosmetically treated hair is analyzed. Moreover, segmentation is an additional advantage of hair testing which can provide additional useful information.

Comparison of LUCIO®-direct ELISA with CEDIA immunoassay for 'zero tolerance' drug screening in urine as required by the German re-licensing guidelines.

The performance of the previously validated LUCIO(®)-Direct-enzyme linked immunosorbent assay (direct ELISA) screening tests according to forensic guidelines is compared to that of cloned enzyme donor immunoassays (CEDIA) test for drugs of abuse in urine as defined in the new re-licensing German medical and psychological assessment (MPA) guidelines. The MPA screening cut-offs correspond to 10 ng/ml 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH), 50 ng/ml amphetamine and designer amphetamines, 25 ng/ml morphine, codeine and dihydrocodeine, 30 ng/ml benzoylecgonine, 50 ng/ml methadone metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and metabolites of diazepam, oxazepam, bromazepam, alprazolam, flunitrazepam and lorazepam at 50 ng/ml. Average relative sensitivities and relative specificities were 99.7 % and 98.4 % for direct ELISA and 66 % and 91.4 % for CEDIA, respectively.

Comparison of urine and hair testing for drugs of abuse in the control of abstinence in driver's license re-granting.

The purpose of the study was to compare the detection rate of illicit drugs in urine and hair specimens. The samples were taken from subjects trying to regain their revoked driver's license after a drug- or alcohol-related traffic offence. In 2010, we screened 14 000 urine and 3900 hair samples for amphetamines, methamphetamines, cannabinoids, cocaine, opiates, methadone, and benzodiazepines as well as for ethylglucuronide. We used the low threshold values of the new German guidelines for Medical Psychological Assessment (MPA). Positive screening tests were confirmed with gas chromatography-mass spectrometry (GC-MS), gas chromatography-tandem mass spectrometry (GC-MS/MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results show that positivity rates for methamphetamines, MDMA, cocaine, and monoacetylmorphine were 1.7-, 5.7-, 3.8- and 9.3-fold higher in hair than in urine. In contrast, the detection rate for benzodiazepines was higher in urine than in hair (oxazepam, 0.21% versus 0%, nordiazepam 0.10% versus 0.03%). The positivity rate in hair for ethylglucuronide was 6-fold (12.7%) that for urine testing (2.1%). The study reveals that in the control of abstinence in the context of driving license re-granting there are in part large differences of positivity rates for some drugs or metabolites between hair and urine samples. These differences should be kept in mind by physicians and psychologists in traffic medicine who are ordering the drug testing.

Significantly increased detection rate of drugs of abuse in urine following the introduction of new German driving licence re-granting guidelines.

In this paper we present the first assessment of the new German driving licence re-granting medical and psychological assessment (MPA) guidelines by comparing over 3500 urine samples tested under the old MPA cut-offs to over 5000 samples tested under the new MPA cut-offs. Since the enzyme multiplied immunoassay technique (EMIT) technology used previously was not sensitive enough to screen for drugs at such low concentrations, as suggested by the new MPA guidelines, enzyme-linked immunosorbent assay (ELISA) screening kits were used to screen for the drugs of abuse at the new MPA cut-offs. The above comparison revealed significantly increased detection rates of drug use or exposure during the rehabilitation period as follows: 1.61, 2.33, 3.33, and 7 times higher for 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH), morphine, benzoylecgonine and amphetamine respectively. The present MPA guidelines seem to be more effective to detect non-abstinence from drugs of abuse and hence to detecting drivers who do not yet fulfil the MPA requirements to regain their revoked driving licence.

Ethyl glucuronide in hair - A highly effective test for the monitoring of alcohol consumption.

In Germany drink driving offenders lose their license and must prove abstinence for one year in order to regain it. In this paper we assess the newly introduced ethyl glucuronide (EtG) tests in urine and hair in this alcohol abstinence monitoring. 20% (80 out of 386) of the 3cm long hair samples were tested positive for EtG in hair, compared to only 2% (92 out of 4248 samples) in urine in the same time period. Additionally 50% of the samples positive for EtG in hair had EtG values greater than 30pg/mg hair, indicating chronic alcohol consumption in the last three months. This study shows that four EtG tests in 3cm hair lengths reveal a significantly higher percentage of drink driving offenders who fail to be sober in the rehabilitation period, than do six random EtG tests in urine. Presumably, the hair test is more adequate to monitor long term alcohol abstinence than the urine test as defined by the new driving license re-granting medical and psychological assessment (MPA) in Germany.

Validation of a headspace solid-phase microextraction-GC-MS/MS for the determination of ethyl glucuronide in hair according to forensic guidelines.

The analysis of ethyl glucuronide (EtG) in hair is a powerful tool for chronic alcohol abuse control because of the typical wide detection window of the hair matrix and due to the possibility of segmentation, allowing evaluation of alcohol consumption in different periods. Additionally, EtG in hair is often the only diagnostic parameter of choice for alcohol abuse when other clinical parameters such as ALT, AST, gammaGT and CDT (asialotransferrin and disialotransferrin) are in the normal range and EtG in urine negative. In this paper, we describe the development, optimization and validation of a new method based on hair extraction with water, clean-up by solid phase extraction (SPE), derivatization with heptafluorobutyric anhydride and headspace solid-phase microextraction (HS-SPME) in combination with GC-MS/MS according to forensic guidelines. The assay linearity of EtG was confirmed over the range from 2.8 to 1000 pg/mg hair, with a coefficient of determination (r(2)) above 0.999. The LLOQ was 2.8 pg/mg and the LLOD was 0.6 pg/mg. An error profile calculated according to the "Guide to the Expression of Uncertainty in Measurement" (GUM) at 99% confidence intervals for the range 5-750 pg/mg hair did not exceed 10%. This range corresponds to more than 98% of the positive samples analysed.