Pregabalin-associated myoclonic encephalopathy without evidence of drug accumulation in a patient with acute renal failure.

Pregabalin, used for treating partial epilepsy and neuropathic pain, is usually well tolerated. Patients with impaired renal function are at risk to develop more serious adverse events. A 64-year-old woman was admitted in the Emergency Department for altered consciousness and abnormal movements. She recently started to take pregabalin (150 mg/day) for neuropathic pain. The drug was withdrawn 36 h before hospitalization following worsening of neurological symptoms. At physical examination, myoclonus was noted as main finding in the limbs and head, with encephalopathy. Laboratory investigations revealed acute renal failure with serum creatinine at 451.3 µmol/l. Urine output was preserved. After supportive care alone, myoclonus resolved after 24 h and consciousness was normal after 48 h. Renal function was also recovered. At the time of admission, the concentration of plasma pregabalin was 3.42 µg/ml, within therapeutic range. The calculated terminal elimination half-life was 11.5 h. Pregabalin-induced myoclonus may not be strictly related to drug accumulation in acute renal failure, with the possibility of a threshold phenomenon.

Longitudinal study on the prevalence of benzodiazepine (mis)use in a prison: importance of the analytical strategy.

AIMS: This study evaluates the suitability of gas chromatographic-mass spectrometric (GC-MS) analysis to follow-up the extent of benzodiazepine (mis)use in a Belgian prison population and compares it to other analytical strategies (e.g. screening followed by confirmation of the positive samples). DESIGN AND PARTICIPANTS: From February to August 1998, 598 persons were jailed of which 188 (31.4% of the incoming detainees) volunteered to be screened. Urine samples (530 in total) were collected on the day of arrival and after 14, 30 and 90 days of imprisonment. MEASUREMENTS: All samples were screened by EMIT(R) for benzodiazepines and analysed subsequently by GC-MS. FINDINGS: EMIT(R) screening yielded 117 (22.1%) positive samples, a number which increased to 174 (32.8%) after GC-MS analysis. Of these 174 GC-MS positive samples, 119 (68.4%) contained one benzodiazepine while for the remaining samples multiple benzodiazepine (mis)use could be demonstrated. A significant increase in benzodiazepine (mis)use was indicated only from day 0 to day 14 based on the GC-MS results but not on the immunoassay results, even when the latter were complemented with GC-MS analysis of the positively screened samples. The GC-MS data also demonstrated that benzodiazepines are mainly (mis)used by subjects on benzodiazepine prescription as almost 50% of these subjects took additional non-prescribed benzodiazepines. During GC-MS analysis other drugs were co-extracted unintentionally and chromatographed and 23.9% of the volunteers were positive for illegal drugs on the day of arrival. CONCLUSION: Immunoassay results yield an underestimation of the problem of benzodiazepine (mis)use in prison due to the high false negative rate. GC-MS analysis of all samples therefore is the recommended strategy for this type of longitudinal study as it yields more correct and detailed information than the immunoassay results.

Analysis of flecainide and two metabolites in biological specimens by HPLC: application to a fatal intoxication.

A few days after her admittance to a hospital for a suicide attempt with benzodiazepines, a 15-year-old girl was found dead in bed. At autopsy, no specific anatomo-pathologic cause of death was identified. Systematic toxicological analysis (HPLC-DAD, GC-NPD, and GC-MS) of postmortem blood and urine revealed the presence of high concentrations of flecainide and its two major metabolites. Flecainide is a class IC anti-arrhythmic drug causing a decreased intracardiac conduction velocity in all parts of the heart. To identify and quantitate flecainide together with its metabolites in blood, urine, and other toxicologically relevant matrices, a new method was developed using high-performance liquid chromatography with diode-array detection. All compounds were separated on a Hypersil BDS phenyl column using water, methanol, and 1.5M ammonium acetate in a gradient system. Chromatographic analysis was preceded by an optimized solid-phase extraction procedure on RP-C18 extraction columns. The flecainide concentrations in blood and urine were 18.73 and 28.3 mg/L, respectively, and the metabolites were detected only in urine at the following concentrations: 9.4 mg/L for meta-O-dealkylated flecainide and 8.59 mg/L for meta-O-dealkylated flecainide lactam. Based on these results, it was concluded that the suicide was consistent with an overdose of this anti-arrhythmic drug.

Sensitive gas chromatographic--mass spectrometric screening of acetylated benzodiazepines.

GC-MS screening conditions were developed for 15 low-dosed benzodiazepines, covering alprazolam, flunitrazepam, flurazepam, ketazolam, lorazepam and triazolam, and the corresponding metabolites alpha-hydroxyalprazolam, 4-hydroxyalprazolam; 7-aminoflunitrazepam, desmethylflunitrazepam, 7-aminodesmethylflunitrazepam; hydroxyethylflurazepam, N-desalkylflurazepam; oxazepam and alpha-hydroxytriazolam, respectively. Benzodiazepines are analyzed on a polydimethylsiloxane column in both the scan and the multiple ion monitoring modes using on-column injection to attain maximal sensitivity. The reactive compounds are acetylated with pyridine and acetic anhydride for 20 min. The derivatives are stable for at least 4 days. The relative standard deviation observed with standard compounds at the low nanogram-level ranged from 1.13 to 4.87% within-day and from 1.12 to 4.94% between-day. Unequivocal identification potential, high chromatographic resolution and sensitivity are combined with minimal thermal degradation. The presented screening conditions provide the basis for a unique routine screening method for low-dosed benzodiazepines with a broad polarity range.

Simultaneous determination of fifteen low-dosed benzodiazepines in human urine by solid-phase extraction and gas chromatography-mass spectrometry.

A gas chromatographic-mass spectrometric method was developed for the simultaneous analysis of 15 low-dosed benzodiazepines, both parent compounds and their corresponding metabolites, in human urine. The target compounds are alprazolam, alpha-hydroxyalprazolam, 4-hydroxyalprazolam, flunitrazepam, 7-aminoflunitrazepam, desmethylflunitrazepam, flurazepam, hydroxyethylflurazepam, nitrogen-desalkylflurazepam, ketazolam, oxazepam, lormetazepam, lorazepam, triazolam and alpha-hydroxytriazolam. Nitrogen-methylclonazepam is used as the internal standard. The urine sample preparation involves enzymatic hydrolysis of the conjugated metabolites with Helix pomatia beta-glucuronidase for 1 h at 56 degrees C followed by solid-phase extraction on a phenyl-type column. The extracted benzodiazepines are subsequently analyzed on a polydimethylsiloxane column using on-column injection to enhance sensitivity. The extraction efficiency exceeded 80% for all compounds except for oxazepam, lorazepam and 4-hydroxyalprazolam which had recoveries of about 60%. The LODs ranged from 13 to 30 ng/ml in the scan mode and from 1.0 to 1.7 ng/ml in the selected ion monitoring (SIM) mode. Linear calibration curves were obtained in the concentration ranges from 50 to 1000 ng/ml in the scan mode and from 5 to 100 ng/ml in the SIM mode. The within-day and day-to-day relative standard deviations at three different concentrations never exceeded 15%.

Analysis of fenthion in postmortem samples by HPLC with diode-array detection and GC-MS using solid-phase extraction.

Fenthion (O,O-dimethyl-O-[3-methyl-4-(methylthio)-phenyl]-thiophos-phate ) is an organophosphate insecticide. A specific method to quantitate fenthion in postmortem matrices with solid-phase extraction combined with high-performance liquid chromatography-diode-array detection (HPLC-DAD) and gas chromatography-mass spectrometry (GC-MS) is presented. Fenitrothion (O,O-dimethyl-O-[3-methyl-4-nitrophenyl]-thiophosphate) is selected as the internal standard. For sample cleanup, a simple but selective solid-phase extraction is chosen after comparison with traditional liquid-liquid extraction procedures. Homogenized and appropriately diluted aqueous samples are applied, and the analytes are desorbed with 5 mL of dichloromethane. Aliquots of the extract are used for HPLC-DAD and GC-MS analysis, Liquid and GC conditions are as follows: gradient elution with a mixture of methanol and water (10:90 to 90:10, v/v) containing 0.0125M NaOH on an Aluspher RP-Select B column monitoring at 250 nm, and temperature programming from 60 to 300 degrees C on a dimethylpolysiloxane column in the SCAN mode, respectively. This method is applied to a suicidal case involving unsuspected acute intoxication with fenthion (concentration in blood, 3.8 micrograms/mL).