Monitoring of benzodiazepines (clobazam, diazepam and their main active metabolites) in human plasma by column-switching high-performance liquid chromatography

[Workplace testing of drugs of abuse and psychotropic drugs]

In France, workplace testing of drugs of abuse and psychotropic drugs is rarely performed; meanwhile it is a major public health problem. Furthermore, France is the European country that has been associated with the highest increase of the use of drugs of abuse, particularly cannabis. So workplace biological screening of drugs of abuse and of psychotropic drugs exposure is of major concern. New analytical techniques have been developed during the last years. The authors will consider analytical screening of drugs of abuse and particularly the comparison of analytical techniques applied to urine and saliva. The advantages and the disadvantages of these two matrices will be considered. Urinary and blood quantification will be reviewed, but also the interest of hair testing to explore chronic exposure. The research of psychotropic drugs in biological fluids is also a part of this paper. New analytical trends are promising and complete analysis of these substances will be soon routinely possible in blood using a single spot test.

Antiepileptic drugs--best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Although no randomized studies have demonstrated a positive impact of therapeutic drug monitoring (TDM) on clinical outcome in epilepsy, evidence from nonrandomized studies and everyday clinical experience does indicate that measuring serum concentrations of old and new generation antiepileptic drugs (AEDs) can have a valuable role in guiding patient management provided that concentrations are measured with a clear indication and are interpreted critically, taking into account the whole clinical context. Situations in which AED measurements are most likely to be of benefit include (1) when a person has attained the desired clinical outcome, to establish an individual therapeutic concentration which can be used at subsequent times to assess potential causes for a change in drug response; (2) as an aid in the diagnosis of clinical toxicity; (3) to assess compliance, particularly in patients with uncontrolled seizures or breakthrough seizures; (4) to guide dosage adjustment in situations associated with increased pharmacokinetic variability (e.g., children, the elderly, patients with associated diseases, drug formulation changes); (5) when a potentially important pharmacokinetic change is anticipated (e.g., in pregnancy, or when an interacting drug is added or removed); (6) to guide dose adjustments for AEDs with dose-dependent pharmacokinetics, particularly phenytoin.

Development of a validated HPLC method for the determination of four 1,4-benzodiazepines in human biological fluids

A simple and sensitive HPLC method was developed and validated for the determination of four frequently prescribed 1,4-benzodiazepines: alprazolam (ALP), bromazepam (BRZ), diazepam (DZP), and flunitrazepam (FNZ). Separation was achieved on an Inertsil C8 analytical (250 mm x 4 mm, 5 microm) column, after selective extraction of benzodiazepine drugs from biological matrices by means of SPE. Isocratic elution was performed with a mobile phase consisting of CH3COONH4, 0.05 M CH3OH, and CH3CN (33:57:10 by volume). Quantification was performed at 240 nm with mefenamic acid (6 ng/microL) as the internal standard. DSC-18 Supelco cartridges provided high absolute recoveries (81-115%). The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 8) and between-day precision (n = 8) revealed RSD <12%. Recoveries from biological samples ranged from 81.2 to 115%. The detection limit of the method was calculated as 3.3-10.2 ng in blood plasma and 2.6-12.6 ng in urine for 20 microL injection volume. The method was applied to spiked biological matrices. Moreover, the method was applied to real samples of urine after an oral administration.

Simultaneous determination of clobazam and its major metabolite in human plasma by a rapid HPLC method

A rapid and specific HPLC method has been developed and validated for simultaneous determination of clobazam, the anticonvulsant agent, and its major metabolite in human plasma. The sample preparation was a liquid-liquid extraction with tuloene yielding almost near 100% recoveries of two compounds. Chromatographic separation was achieved with a Chromolith Performance RP-18e 100 mm x 4.6mm column, using a mixture of a phosphate buffer (pH 3.5; 10mM)-acetonitrile (70:30, v/v), in isocratic mode at 2 ml/min at a detection wave-length of 228 nm. The calibration curves were linear (r(2)>0.998) in the concentration range of 5-450 ng ml(-1). The lower limit of quantification was 5 ng ml(-1) for two compounds studied. The within- and between-day precisions in the measurement of QC samples at four tested concentrations were in the range of 0.89-9.1% and 2.1-10.1% R.S.D., respectively. The developed procedure was applied to assess the pharmacokinetics of clobazam and its major metabolite following administration of a single 10mg oral dose of clobazam to healthy volunteers.

Forensic intoxication with clobazam: HPLC/DAD/MSD analysis

Clobazam (Castillium, Urbanil), a benzodiazepine often used as an anxiolytic and in the treatment of epilepsy, is considered a relatively safe drug. The authors present a fatal case with a 49-year-old female, found dead at home. She had been undergoing psychiatric treatment and was a chronic alcoholic. The autopsy findings were unremarkable, except for multivisceral congestion, steatosis and a small piece of a plastic blister pack in the stomach. Bronchopneumonia, bronchitis and bronchiolitis were also diagnosed. Anhigh-performance liquid chromatography (HPLC)/diode array detector (DAD)/mass spectrometry detection (MSD) with electrospray method was developed in order to detect, confirm and quantify clobazam in the post-mortem samples. In the chromatographic separation, a reversed-phase column C18 (2.1 x 150 mm, 3.5 microm) was used with a mobile phase of methanol and water, at a 0.25 ml/min flow rate. Carbonate buffer (pH 10.5) and 20 microl of prazepam (100 microg/ml) as internal standard were added to the samples. A simple and reliable liquid-liquid extraction method for the determination of clobazam in post-mortem samples was described. Calibration curves for clobazam were performed in blood, achieving linearity between 0.01 and 10 microg/ml and a detection limit of 1.0 ng/ml. The clobazam concentration found in post-mortem blood was 3.9 microg/ml, higher than the reported therapeutic concentration (0.1-0.4 microg/ml). The simultaneous acquisition by photodiode array detection and mass spectrometry detection results allowed benzodiazepines to be identified with sufficient certainty. An examination of all the available information suggested that death resulted from respiratory depression due to clobazam toxicity.

Determination of antiepileptic drugs in biological material

Current analytical methodologies applied to the determination of antiepileptic drugs in biological material are reviewed. The role of chromatographic techniques is emphasized. Special attention is focused on new chemical entities as well as current trends such as high-speed liquid chromatographic techniques, hyphenated techniques and electrochromatography techniques. A review with 542 references.

Direct LC analysis of five benzodiazepines in human urine and plasma using an ADS restricted access extraction column

An alkyl-diol-silica (ADS) precolumn was used for the direct and on-line extraction of several benzodiazepines from serum and urine. The protein component of the biological sample was flushed through the ADS column, while simultaneously extracting the benzodiazepine compounds in the pores of the ADS stationary phase. The role of hydrophobic interactions in the extraction mechanism was confirmed. Column switching was employed to elute the extracted analytes from the ADS column into a high-performance liquid chromatography reverse-phase C18 column for the isocratic separation and UV detection of the benzodiazepines. Sample preconcentration via large volume injections was possible, improving the limits of detection. The calculated clonazepam, oxazepam, temazepam, nordazepam and diazepam detection limits were 38.8, 24.2, 31.7, 31.3, 45.0 ng/ml in serum, respectively, and 48.4, 24.5, 31.7, 33.1, 52.9 ng/ml for urine, respectively. The method was linear over the range of 50-10000 ng/ml in both matrices with an average linear coefficient (R(2)) value of 0.9918. The injection repeatability and intra-assay precision of the method were evaluated over ten injections, resulting in a percent relative standard deviation <5%. The ADS extraction column was robust, providing many direct injections of biological fluids for the extraction and subsequent determination of benzodiazepines.

High-performance liquid chromatographic determination of diazepam in plasma of children with severe malaria

A sensitive, selective and reproducible reversed-phase HPLC method with ultraviolet detection was developed for the quantification of diazepam in small plasma samples from children with severe malaria. The method involves plasma deproteinization with acetonitrile, followed by liquid-liquid extraction with ethyl acetate-n-hexane. Diazepam was eluted at ambient temperatures from a reversed-phase C18 column with an acidic (pH 3.5) aqueous mobile phase (10 mM KH2PO4-acetonitrile, 69:31, v/v). Calibration curves in spiked plasma were linear from 10 to 200 ng (r2 > or = 0.99). The limit of detection was 5.0 ng/ml, and relative recoveries at 25 and 180 ng were >87%. Intra- and inter-assay relative standard deviations were <15%. There was no interference from drugs commonly administered to children with severe malaria (phenobarbitone, phenytoin, chloroquine, quinine, sulfadoxine, pyrimethamine, halofantrine, cycloguanil, chlorcycloguanil, acetaminophen and salicylate). This method has been used for monitoring plasma diazepam concentrations in children with seizures associated with severe malaria.

Normal-phase high-performance liquid chromatographic separations using ethoxynonafluorobutane as hexane alternative. I. Analytical and chiral applications

A novel, environmentally friendly, fluorinated solvent--ethoxynonafluorobutane--has been used to replace n-hexane in normal-phase HPLC applications. Fast gradients of methanol in ethoxynonafluorobutane on a cyano column have been successfully applied to the separation of steroids, benzodiazepines, NSAIDs, tricyclic antidepressants, beta-adrenergic blocking agents and mixtures of purines and pyrimidines. Small amounts of triethylamine and trifluoroacetic acid added to such gradients significantly improved peak shape and column performance for basic and acidic solutes. Ethoxynonafluorobutane and its mixtures with methanol have also been demonstrated to have a unique selectivity in chiral HPLC applications.

Simple and sensitive high-performance liquid chromatographic method for the determination of 1,5-benzodiazepine clobazam and its active metabolite N-desmethylclobazam in human serum and urine with application to 1,4-benzodiazepines analysis

A HPLC-UV determination of clobazam and N-desmethylclobazam in human serum and urine is presented. After simple liquid-liquid extraction with dichloromethane the compounds and an internal standard diazepam were separated on a Supelcosil LC-8-DB column at ambient temperature under isocratic conditions using the mobile phase: CH3CN-water-0.5 M KH2PO4-H3PO4 (440:540:20:0.4, v/v and 360:580:60:0.4, v/v for serum and urine, respectively). The detection was performed at 228 nm with limits of quantification of 2 ng/ml for serum and 1 ng/ml for urine. Relative standard deviations for intra- and inter-assay precision were found below 8% for both compounds for all the tested concentrations. The described procedure may be easily adapted for several 1,4-benzodiazepines.

Chromatography of guanidino compounds

Guanidino compounds involved in the urea and guanidine cycles have been found in serum of nephritic patients, and some guanidino compounds have been suspected to be uremic toxins. The simultaneous analysis of naturally occurring metabolites is important for diagnosis of diseases. In this review, liquid chromatographic analysis of natural metabolites of guanidino compounds are described. the information about arginine as a precursor of nitric oxide are included. The reports of pharmaceutical compounds having a guanidino group, peptides containing arginine and aminoglycosides are summarized in Table 1.

Chromatographic screening techniques in systematic toxicological analysis

A review of techniques used to screen biological specimens for the presence of drugs was conducted with particular reference to systematic toxicological analysis. Extraction systems of both the liquid-liquid and solid-phase type show little apparent difference in their relative ability to extract a range of drugs according to their physio-chemical properties, although mixed-phase SPE extraction is a preferred technique for GC-based applications, and liquid-liquid were preferred for HPLC-based applications. No one chromatographic system has been shown to be capable of detecting a full range of common drugs of abuse, and common ethical drugs, hence two or more assays are required for laboratories wishing to cover a reasonably comprehensive range of drugs of toxicological significance. While immunoassays are invariably used to screen for drugs of abuse, chromatographic systems relying on derivatization and capable of extracting both acidic and basic drugs would be capable of screening a limited range of targeted drugs. Drugs most difficult to detect in systematic toxicological analysis include LSD, psilocin, THC and its metabolites, fentanyl and its designer derivatives, some potent opiates, potent benzodiazepines and some potent neuroleptics, many of the newer anti-convulsants, alkaloids colchicine, amantins, aflatoxins, antineoplastics, coumarin-based anti-coagulants, and a number of cardiovascular drugs. The widespread use of LC-MS and LC-MS-MS for specific drug detection and the emergence of capillary electrophoresis linked to MS and MS-MS provide an exciting possibility for the future to increase the range of drugs detected in any one chromatographic screening system.

Determination of benzodiazepine in tablets studied by thermal desorption gas chromatography

Thermal desorption gas chromatography (TDGC) was applied to the analysis of 13 kinds of tablets containing different benzodiazepines (BZDs). An aliquot of ground tablet sample (0.1-1 mg), weighed into a platinum sample cup, was placed in a furnace pyrolyzer where the sample was heated up to a suitable temperature (150-500 degrees C) so that BZD was desorbed from the sample powder. The desorbed components of BZDs were immediately transferred into a separation column by a helium carrier gas without using any trapping techniques. The desorbed components were identified by TDGC-mass spectrometry. Among various BZDs, fludiazepam, nimetazepam and mexazolam in tablet samples were determined by the present method. Thus, the results obtained were in good agreement with the specified values. Correlation coefficients of the calibration lines for the three BZDs' ranged from 0.997 to 0.999 for several micrograms to about 10 microg of the components. Relative standard deviations of this method were < 4.1% for 4 or 5 runs.

Direct determination of stability of protease inhibitors in plasma by HPLC with automated column-switching

Automated column-switching HPLC methods were developed and utilized for the direct analyses of three hydroxamic acid based metalloprotease inhibitors in rat plasma. These column-switching methods involved the use of a restricted-access media (RAM) precolumn and a column-switching valve, allowing the complete automation of sample preparation and HPLC. The plasma samples were directly injected onto a precolumn packed with SPS/ODS stationary phase and then backflushed onto an ODS analytical column using a 6-port column-switching device. The drug stability in rat plasma was determined using both the automated and traditional HPLC methods. The results obtained from the automated column-switching methods were in good agreement with those from traditional methods that involve sequential protein precipitation, liquid extraction, solvent evaporation, and sample reconstitution. In addition to the elimination of labor-intensive and time-consuming sample preparation procedures, the column-switching methods allowed on-line analyte enrichment and accurate determination of drug stability in plasma with detection limits in the range of 10-20 ng/ml(-1). This work represents, for the first time, a drug stability study in plasma by automated column-switching HPLC technique with the use of a RAM column. Our column-switching methods can be readily adapted to any existing HPLC system with minimal hardware modification.

Rapid analysis of guanidino compounds in serum from nephritic patients using column-switching with isocratic elution

The rapid method for baseline separation of ten guanidino compounds in serum from nephritic patients was designed using a single eluent with a column switching system. A porous graphitic carbon column and an octadecyl-bonded silica gel columns were used, (50 mm x 4.6 mm i.d.). Separation was completed within 15 min. The stable baseline permitted highly sensitive detection with excellent reproducibility. The system was applied to analyze guanidino compounds in sera from 175 nephritic patients. The hemodialysis process could not completely eliminate guanidino compounds, and the degree of removal varied between patients. The correlation among metabolites indicated the differences in disease.

Methods for the measurement of benzodiazepines in biological samples

A review of methods for the measurement of benzodiazepines in biological specimens published over the last five years is presented. A range of immunoassay procedures using EIA, ELISA, FPIA, agglutination or kinetic interaction of microparticles, or RIA methods are now available. Cross reactivities to benzodiazepines are variable such that no one kit will recognise all benzodiazepines and their relevant metabolites at concentrations likely to be encountered during therapeutic use. Prior hydrolysis of urine to convert glucuronide metabolites to immunoreactive substances improves detection limits for many benzodiazepines. Several radioreceptor assays have now been published and show good sensitivity and specificity to benzodiazepines and offer the advantage (over immunoassay) of being able to detect these drugs with equal sensitivity. Solvent extraction techniques using a variety of solvents were still popular and offer acceptable recoveries and lack of significant interference from other substances. A number of papers describing solid phase extraction procedures were also published. Direct injection of specimens into a HPLC column with back flushing were also successfully described. Seventy two chromatographic methods using HPLC, LC-MS, GC and GC-MS methods were reviewed. HPLC was able to achieve detection limits for many benzodiazepines using UV or DAD detection down to 1-2 ng/ml using 1-2 ml of urine or serum (blood). ECD detectors gave detection limits better than 1 ng/ml from 1 ml of specimen, which was an order of magnitude lower than for NPD. EI-MS offered similar sensitivity, whilst NCI-MS was capable of detection down to 0.1 ng/ml. Methods suitable for the separation of enantiomers of benzodiazepines have been described using HPLC. Electrokinetic micellar chromatography has also been shown to be capable of the analysis of benzodiazepines in urine.

Screening for drugs of abuse (II): Cannabinoids, lysergic acid diethylamide, buprenorphine, methadone, barbiturates, benzodiazepines and other drugs

Requirements for the provision of an efficient and reliable service for drugs of abuse screening in urine have been summarized in Part I of this review. The requirements included rapid turn-around times, good communications between requesting clinicians and the laboratory, and participation in quality assessment schemes. In addition, the need for checking/confirmation of positive results obtained for preliminary screening methods was stressed. This aspect of the service has assumed even greater importance with widespread use of dip-stick technology and the increasing number of reasons for which drug screening is performed. Many of these additional uses of drug screening have possible serious legal implications, for example, screening school pupils, professional footballers, parents involved in child custody cases, persons applying for renewal of a driving licence after disqualification for a drug-related offence, doctors seeking re-registration after removal for drug abuse, and checking for compliance with terms of probation orders; as well as pre-employment screening and work-place testing. In many cases these requests will be received from a general practitioner or drug clinic with no indication of the reason for which testing has been requested. This also raises the serious problems of a chain of custody, provision of two samples, stability of samples, and secure and lengthy storage of samples in the laboratory-samples may be requested by legal authorities several months after the initial testing. The need for confirmation of positive results is now widely accepted but it may be equally important to confirm unexpected negative results. Failure to detect the presence of maintenance drugs may lead to the patient being discharged from a drug treatment clinic and, if attendance at the clinic is one of the terms of continued employment, to dismissal. It seems likely that increasing abuse of drugs and the efforts of regulatory authorities to control this, will lead to the manufacture of more designer drugs. Production of substituted phenethylamines was facilitated by the drug makers' cook book, 'PIHKAL' (Phenethylamines I Have Known And Loved) by Dr Alexander Shulgin and Ann Shulgin, and production of substituted tryptamines is promised in their next book, TIHKAL. Looking to the future, laboratories will need to ensure that they can detect and quantitate an ever-increasing number of drugs and related substances. The question of confidence in results of drugs of abuse testing raised in 1993 by Watson has assumed even greater importance as a result of attention focused on the OJ Simpson trial in Los Angeles. Toxicological investigations are likely to be challenged more frequently in the future. Even if analyses have been performed by GC-MS, there is a need to establish the level of match between the spectrum of the unknown substance and a library spectrum which is considered acceptable for legal purposes. It will also be essential to ensure that computer libraries contain spectra for all substances likely to be encountered in drugs of abuse screening.

Micellar electrokinetic capillary chromatography of benzodiazepine antiepileptics and their desmethyl metabolites in blood

A fast and reliable method for the MEKC separation and determination of benzodiazepine antipileptics and their active metabolites in serum has been developed, using a separation buffer composed of borate (pH 9.5), SDS (18 mM), and acetonitrile (14%) as an organic modifier. The method is sensitive enough to be used clinically with a precision of less than 3% for the analysis of nitrazepam, clonazepam, clobazam, diazepam and their desmethyl metabolites in serum.