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In 2013, the National Safety Council's Alcohol Drugs and Impairment Division added zolpidem and carisoprodol and its metabolite meprobamate to the list of Tier 1 drugs that should be tested for in all suspected drug impaired driving and motor vehicle fatality investigations. We describe the validation of an enzyme linked immunosorbent assays (ELISA) for both drugs in whole blood, and the utilization of the ELISA to assess their positivity in a sample of 322 suspected impaired driving cases that was retrospectively screened using the validated assays. The occurrence of carisoprodol/meprobamate was found to be 1.2%, and for zolpidem, 1.6%. In addition, we analyzed a large dataset (n = 1,672) of Driving Under the Influence of Drugs (DUID) test results from a laboratory performing high volume DUID testing to assess the frequency of detection of both drugs after implementing the expanded NSC scope. Carisoprodol or meprobamate were found positive in 5.9% (n = 99) of these samples, while zolpidem was found positive in 5.3% (n = 89) in drivers who in many cases had been found to be negative for other drugs. Carisoprodol and zolpidem are both potent CNS depressants and are appropriate additions to the recommended NSC scope of testing., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Carisoprodol and meprobamate are centrally acting muscle relaxant/anxiolytic drugs that can exist in a parent-metabolite relationship (carisoprodol → meprobamate) or as a separate pharmaceutical preparation (meprobamate aka Equanil, others). The monitoring of the use of these drugs has both clinical and forensic applications in pain management applications and in overdose situations. LC-MS/MS is used to analyze urine or plasma/serum extracts with deuterated analogs of each analyte as internal standards to ensure accurate quantitation and control for any potential matrix effects. Positive ion electrospray is used to introduce the analytes into the mass spectrometer. Selected reaction monitoring of two product ions for each analyte allows for the calculation of ion ratios which ensures correct identification of each analyte, while a matrix-matched calibration curve is used for quantitation.

A multidrug fatality involving sumatriptan is reported. Sumatriptan is a tryptamine derivative that acts at 5-HT(1B/1D) receptors and is used for the treatment of migraines. The decedent was a 21-year-old white female found dead in bed by her spouse. No signs of physical trauma were observed and a large number of prescription medications were discovered at the scene. Toxicological analysis of the central blood revealed sumatriptan at a concentration of 1.03 mg/L. Following therapeutic dosing guidelines, sumatriptan concentrations do not exceed 0.095 mg/L. Sumatriptan was isolated by solid-phase extraction and analyzed using liquid chromatography-tandem mass spectrometry in multiple reaction monitoring mode. A tissue distribution study was completed with the following concentrations measured: 0.61 mg/L in femoral blood, 0.56 mg/L in iliac blood, 5.01 mg/L in urine, 0.51 mg/kg in liver, 3.66 mg/kg in kidney, 0.09 mg/kg in heart, 0.32 mg/kg in spleen, 0.01 mg/kg in brain, 15.99 mg/kg in lung and 78.54 mg/45 mL in the stomach contents. Carisoprodol, meprobamate, fluoxetine, doxylamine, orphenadrine, dextromethorphan and hydroxyzine were also present in the blood at the following concentrations: 3.35, 2.36, 0.63, 0.19, 0.06, 0.55 and 0.16 mg/L. The medical examiner ruled the cause of death as acute mixed drug toxicity and the manner of death as accident., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The identification and quantitation of carisoprodol (Soma) and its chief metabolite meprobamate, which is also a clinically prescribed drug, remains a challenge for forensic toxicology laboratories. Carisoprodol and meprobamate are notable for their widespread use as muscle relaxants and their frequent identification in the blood of impaired drivers. Routine screening is possible in both an acidic/neutral pH screen and a traditional basic screen. An improvement in directed testing quantitations was desirable over the current options of an underivatized acidic/neutral extraction or a basic screen, neither of which used ideal internal standards. A new method was developed that utilized a simple protein precipitation, deuterated internal standards and a short 2-min isocratic liquid chromatography separation, followed by multiple reaction monitoring with tandem mass spectrometry. The linear quantitative range for carisoprodol was determined to be 1-35mg/L and for meprobamate was 0.5-50mg/L. The method was validated for specificity and selectivity, matrix effects, and accuracy and precision., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Introduction: Carisoprodol, a frequently used muscle relaxant, can cause potentially fatal intoxications. Conversion to its active metabolite meprobamate is almost solely mediated by cytochrome P450 2C19 (CYP2C19), and mutations in this enzyme could have significant effects on serum concentrations. The objective of this study was to investigate the role of CYP2C19 genetics in mortalities due to carisoprodol intoxication., Methods: The frequencies of CYP2C19 variant alleles were compared between the study group (n = 75) and two control groups, i.e. (1) deaths where carisoprodol was detected in the blood of the deceased, but intoxication was not the cause of death (control group A, n = 38), and (2) a healthy population not using carisoprodol (control group B, n = 185). In the study group and control A, the concentrations of carisoprodol and meprobamate were compared between the different genotype subgroups., Results: The variant allele frequencies of CYP2C19 did not differ significantly between the study group and control groups. Moreover, no statistically significant difference in the concentrations of carisoprodol and meprobamate between the different genotype subgroups was found., Conclusions: This study finds no evidence for an important association between CYP2C19 genetics and mortality risk of carisoprodol. Other factors, such as co-administration with other drugs, likely play a more important role.

Carisoprodol is a therapeutic and occasionally abused centrally acting muscle relaxant. We compare central blood and liver concentrations of carisoprodol and the metabolite meprobamate to concentrations in peripheral blood in 11 medical examiner cases. Specimens were initially screened for alcohol and simple volatiles by gas chromatography (GC)-flame ionization detection headspace analysis, enzyme-linked immunosorbent array for drugs of abuse, and therapeutic drugs by GC-mass spectrometry (MS). Carisoprodol, when detected by the therapeutic drug screen, was confirmed and quantified by a specific GC-MS procedure. The results suggest that when ingested with other medications, carisoprodol may be a contributing factor in death, even when present at therapeutic concentrations. Considering the cases studied, together with previously published therapeutic and fatal concentrations, blood carisoprodol concentrations greater than 15 mg/L and liver concentrations greater than 50 mg/kg may be considered excessive and potentially fatal. Carisoprodol central blood to peripheral blood ratios averaged 1.31 + 0.33 (mean ± standard deviation), and liver to peripheral blood, 2.83 ± 1.51. Meprobamate central blood to peripheral blood ratios averaged 0.92 ± 0.22, and liver to peripheral blood, 1.25 ± 0.69. The low liver to peripheral blood ratio (less than 5), taken together with the low central blood to peripheral blood ratio, is an indicator that both carisoprodol and meprobamate lack the potential to exhibit postmortem redistribution.

Background: Meprobamate is a carbamate, and the main metabolite of carisoprodol. It is used as an anxiolytic agent. Overdose of both drugs produces intoxication that is often serious and sometimes life threatening. However there was until now no immunoassay for the diagnosis of this intoxication., Methods: A chemiluminescent immunoassay for the semi-quantitative measurement of meprobamate in human blood and plasma has recently been developed, using the Evidence Investigator system (Randox®). In this study, the immunoassay was evaluated by testing drug-free (n=10) or spiked whole blood and plasma samples (n=70), and authentic post mortem whole blood samples from deceased patients in which meprobamate was present (n=38) or not (n=10). A previously validated gas chromatography-mass spectrometry (GC-MS) method was used for confirmation and quantification. 97 psychoactive drugs including carisoprodol were analyzed for possible interference., Results: With a cut-off at 0.5 mg/L, specificity, sensitivity and accuracy were 100%, 97.2% and 97.6%, respectively. All the untreated patients presented results under the cut-off. Meprobamate was not detected in three whole blood samples spiked with concentrations under the therapeutic range. In the authentic patients (n=48), there were no false-negative results. A good correlation was found between the immunoassay and GC-MS (r=0.90). Quantitative results of the immunoassay are approximately two-fold lower than GC-MS results. Only carisoprodol presented a cross-reactivity, 38±6.6% at 10 mg/L, and 26±4.8% at 100mg/L., Conclusion: The first meprobamate immunoassay has shown very good specificity, selectivity and accuracy, which allow its use in hospital clinical laboratories for rapid diagnosis of meprobamate (or carisoprodol) intoxications., (Copyright © 2011 Elsevier B.V. All rights reserved.)

We described the development and full validation of rapid and accurate liquid chromatography method, coupled with tandem mass spectrometry detection, for quantification of meprobamate in human plasma with [(13)C-(2)H(3)]-meprobamate as internal standard. Plasma pretreatment involved a one-step protein precipitation with acetonitrile. Separation was performed by reversed-phase chromatography on a Luna MercuryMS C18 (20 mm×4 mm×3 μm) column using a gradient elution mode. The mobile phase was a mix of distilled water containing 0.1% formic acid and acetonitrile containing 0.1% formic acid. The selected reaction monitoring transitions, in electrospray positive ionization, used for quantification were 219.2→158.2 m/z and 223.1→161.1m/z for meprobamate and internal standard, respectively. Qualification transitions were 219.2→97.0 and 223.1→101.1 m/z for meprobamate and internal standard, respectively. The method was linear over the concentration range of 1-300 mg/L. The intra- and inter-day precision values were below 6.4% and accuracy was within 95.3% and 103.6% for all QC levels (5, 75 and 200 mg/L). The lower limit of quantification was 1 mg/L. Total analysis time was reduced to 6 min including sample preparation. The present method is successfully applied to 24/7 clinical toxicology and demonstrated its usefulness to detect meprobamate poisoning., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Clobazam is a benzodiazepine with anti-anxiety and anticonvulsant properties marketed in several countries. Norclobazam, a metabolite of clobazam, has similar pharmacological activity but weaker sedative and tranquilizing effect. The two drugs were detected by GC-MS and determined by HPLC-DAD in the samples from a postmortem case. The femoral blood concentrations of clobazam and norclobazam were 0.72 and 36 μg/mL, respectively. The concentration of the active norclobazam was very high. The sum of both clobazam and norclobazam blood concentration (36.72 μg/mL) was clearly toxic, but was not necessarily fatal. Other associated drugs concentrations were within their therapeutic ranges. Interactions due to drug association were discussed., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

The centrally acting muscle relaxant carisoprodol has previously been shown to cause psychomotor impairment and to have a narrow therapeutic range. In Norway, carisoprodol was therefore reclassified to the highest scheduling level from 1 August 2007 and withdrawn from the market on 1 May 2008. The aim of this study was to examine to what extent this action resulted in reduced numbers of driving under the influence (DUI) cases and forensic autopsies concerning carisoprodol, as well as reduced numbers of contacts to the National Poisons Information Centre (NPIC) in Norway regarding carisoprodol. From 2004 to 2008, carisoprodol (and/or its metabolite meprobamate) was detected in a total of 1261 DUI cases, decreasing from 312 in 2004 to 47 in 2008. During the same period, carisoprodol was detected in 194 forensic autopsies, also here decreasing, from 53 cases in 2004 to 11 cases in 2008. The NPIC received 1180 contacts primarily concerning carisoprodol over this period, decreasing from 267 contacts in 2004 to 87 contacts in 2008. During the same period, the sales figures for carisoprodol decreased dramatically, and we observed a relation between the numbers of DUI cases, forensic autopsies and contacts to the NPIC concerning carisoprodol and the sales figures for the drug. This study showed that the rescheduling and withdrawal of carisoprodol from the Norwegian market had a positive effect on the prevalence of carisoprodol in impaired driving, deaths and contacts regarding intoxications. This, together with previous publications, indicates that the population reflected in our data uses regularly prescribed carisoprodol and, to a lesser degree, drug from an illegal street market.

Carisoprodol and meprobamate are frequently encountered drugs in impaired driving casework. Deuterated internal standards, although preferred, were not available until recently. Earlier published studies report the use of a variety of non-deuterated internal standards, many of which lack the chemical and physical similarities that are desired for quantitative analysis. Carisoprodol and meprobamate were determined in whole blood using solid-phase extraction and gas chromatography-mass spectrometry with benzylcarbamate and meprobamate-d(7) as internal standards. When benzylcarbamate was used as internal standard, the linear ranges for carisoprodol and meprobamate were 0-20 mg/L and 0-40 mg/L, respectively. The linear range increased to 100 mg/L when meprobamate-d(7) was used. Limits of detection for carisoprodol and meprobamate were 0.2 and 0.4 mg/L, respectively, regardless of the internal standard selection. The limit of quantitation for both drugs using either internal standard was 0.4 mg/L. Accuracies using benzylcarbamate and meprobamate-d(7) were 100-106% and 91-100%, respectively. Corresponding values for precision indicated intra-assay coefficients of variation of 2.6-4.3% for benzylcarbamate and 1.0-2.3% for meprobamate-d(7). No carryover was evident at 100 mg/L, the highest concentration tested, and no interferences were observed. Results indicated that either benzylcarbamate or meprobamate-d(7) is a suitable internal standard for quantitative determination of carisoprodol or meprobamate from whole blood.

A rapid, sensitive, and ready-to-use gas chromatography-mass spectrometry method for meprobamate assay using carisoprodol as internal standard is described. The method involves extracting a 0.2-mL sample with chloroform, previously acidified with HCl 0.2N. For the quantitative analysis, we used selected-ion monitoring mode, selecting the ion m/z 144 for quantification of meprobamate and m/z 245 for carisoprodol. Excellent linearity was found between 0 and 200 mg/L plasma. The limit of detection was 0.58 mg/L, and the limit of quantification was 1.93 mg/L. A high reproducibility [intra-assay coefficient of variation (CV) range of 2.3-4.3% and interassay CV range of 5.5-12.3%] and accuracy (intra-assay range of 96.8-112.3% and interassay range of 85.5-99.3%) were observed. Recoveries were concentration-independent (87.0%, 76.2%, and 81.2% for 20, 75 and 150 mg/L, respectively). No interference from endogenous compounds, other metabolites of meprobamate, or frequently coadministered drugs was detected. This sensitive, simple assay for meprobamate in plasma, whole blood, and urine meets the current requirements for bioanalytical assays in overdose cases.

Objective: Meprobamate self-poisoning has been reported as potentially inducing hypotension. We examined the incidence and causes of hypotension induced by this poisoning and its prognosis., Design and Setting: Retrospective observational study conducted in a medical ICU between June 1997 and October 2003. Seventy-four patients admitted for meprobamate poisoning and needing mechanical ventilation were included. Demographic, clinical, and laboratory data were compared between patients with and without hypotension. All echocardiograms recorded in patients with hypotension were reviewed, and left ventricular (LV) and right ventricular (RV) functions were assessed., Results: Twenty-nine (40%) patients exhibited hypotension without any significant difference in age, gender, cardiac history, or meprobamate concentration in blood when compared to patients without hypotension. Base excess was significantly lower in patients with hypotension. Echocardiography demonstrated a hypokinetic state, associating decreased LV ejection fraction (45+/-15%) and cardiac index (2+/-0.7 l min(-1) m(-2)), and increased inferior vena cava diameter. Most patients with hypotension received inotropic drugs by infusion, and were ventilated for significantly longer., Conclusions: Meprobamate self-poisoning induces hypotension, notably related to cardiac failure, in about 40% of cases. This has important therapeutic consequences, as frequent inotropic drug infusion. The mechanisms of cardiac toxicity remain largely unknown, and no predictive factor could be isolated.

Rationale: The active placebo hypothesis states that placebo effects are potentiated when an active drug is administered., Objective: This hypothesis was tested in an experiment where information about the effect of a drug was combined with administration of an active drug or placebo., Methods: Information that a drug acted as a relaxant, a stimulant, or as a placebo was crossed with oral administration of a relaxant drug (700 mg carisoprodol), a stimulant drug (400 mg caffeine) or placebo (lactose) in healthy volunteers ( n=94). Dependent variables were subjective and physiological measures of arousal, as well as serum carisoprodol and caffeine levels. Data were collected from 15 to 280 min after administration of drug or placebo., Results: Caffeine increased alertness, systolic and diastolic blood pressure, startle blink reflexes, and skin conductance responses. Subjects were calmer after carisoprodol, and heart rate was increased. There was a positive correlation between increased arousal and carisoprodol levels when stimulant information had been provided. However, this was only seen when carisoprodol levels were very low. There was no evidence that caffeine modulated the placebo response., Conclusions: Active placebo responses were seen only transiently when carisoprodol levels were low, and only in the subjective arousal data. Caffeine did not support active placebo responses. The overall findings did not favour the active placebo hypothesis.

Our aim was to explore the agreement between clinically collected information on purported drug intake and plasma data in intentional drug overdose. We included all subjects with intentional drug overdose above 15 years of age consecutively admitted to the Emergency Department of the University Hospital during 4 months. Information about drugs used and sources of this information was collected and compared to presence of drug in plasma, concerning four drugs with high toxic potential (tricyclic antidepressants, meprobamate, paracetamol and ethanol). Sensitivity, specificity, predictive positive and negative values of all sources of information pooled were assessed for each drug. 413 intentional drug overdoses were included, 66% with more than one drug. According to clinical information, 8% took tricyclic antidepressants, 11% meprobamate, 9% paracetamol and 41% ethanol. Systematic plasma assays confirmed this in 59% of cases for tricyclic antidepressants, 76% for meprobamate and ethanol, and 77% for paracetamol. Plasma concentrations were considered toxic in 28% of cases for tricyclic antidepressants, 65% for meprobamate, 43% for ethanol and never for paracetamol. Tricyclic antidepressants and meprobamate were found unexpectedly in 3%, paracetamol in 7% and ethanol in 6%. Toxic concentrations were found only with meprobamate. The risk of erroneous, clinically collected information was greater by excess (25 to 40% false positives) than by lack (3 to 7% false negatives). Thus, the consequences of erroneous, clinically collected information were probably more excess cost for the institution than medical risk for the patients. However these results found at the population level may not be true at an individual level.

Background: Carisoprodol is a centrally acting muscle relaxant commonly used for lower back pain. It is a drug of abuse and has been detected among impaired drivers. Carisoprodol's active metabolite meprobamate is thought to act through the GABA(A) receptor complex and produces a well-known impairing effect. It is unclear whether therapeutic intake of carisoprodol leads to impairment, and the effect of supratherapeutic doses has not been investigated. Possible impairment could further be a product of the parent drug and/or the metabolite meprobamate. The present study aimed to investigate if carisoprodol had an impairing effect by it self., Methods: From the database at the Norwegian Institute of Public Health, Division for Forensic Toxicology and Drug Abuse 62 cases containing carisoprodol and meprobamate as only drugs were identified. These cases constituted our material., Results: Impaired drivers (73%) had higher blood carisoprodol concentration than not impaired drivers (27%), but no difference in blood meprobamate concentration was found for all the drivers viewed together. Amongst occasional users of carisoprodol, however, there was difference in blood meprobamate concentration between not impaired and impaired drivers. The risk of being judged impaired rose with increasing blood carisoprodol concentration, but not with increasing blood meprobamate concentration. The clinical effects of carisoprodol as measured by the clinical test for impairment (CTI) resembled those of benzodiazepines with some important differences such as tachycardia, involuntary movements, hand tremor and horizontal gaze nystagmus, which may be specific carisoprodol effects., Conclusion: Carisoprodol probably has an impairing effect by itself, at least at blood concentration levels above which can be seen after therapeutic intake of the drug.

Carisoprodol is metabolized to meprobamate by the cytochrome P450 enzyme CYP2C19, encoded by the polymorphic CYP2C19 gene. Most studies on carisoprodol metabolism have been carried out on individuals phenotyped for CYP2C19 activity using the probe drug S-mephenytoin. We aimed to investigate whether the ratio of carisoprodol to meprobamate in a 'real life' setting could be predicted by CYP2C19 genotype or, more specifically, if high carisoprodol : meprobamate ratios in drugged drivers could be ascribed to the presence of mutant CYP2C19 alleles. From original material comprising 358 blood samples from apprehended drivers, two polarized groups were selected; a high-ratio group of 11 subjects where the carisoprodol : meprobamate ratio was >1 and a low-ratio control group of 23 subjects where the ratio was <0.31. Genotyping was carried out for the CYP2C19*2, CYP2C19*3 and CYP2C19*4 alleles. DNA samples from 94 healthy blood donors were used as reference material. The number of mutant alleles in the high-ratio and low-ratio groups was significantly higher and lower, respectively, than in the reference material. The increased number of mutant alleles in the high-ratio group was not due to the presence of many poor metabolizers, but to a high number of heterozygous individuals with the genotype CYP2C19*1/*2. This result indicates a gene dosage effect where the carisoprodol : meprobamate ratio reflects the number of active CYP2C19 alleles. The metabolism of carisoprodol to meprobamate is dependent on CYP2C19 genotype. Heterozygous individuals with the CYP2C19*1/*2 genotype have a reduced capacity for metabolizing carisoprodol, and should probably be regarded as intermediate metabolizers of this drug.

Implementation of regulations to control the prescribing of benzodiazepines in New York State in 1989 resulted in a 55% decrease in benzodiazepine prescribing, with a concomitant increase in the rates of prescribing older sedative-hypnotic compounds such as butabarbital (30% increase) and meprobamate (125% increase). In a double-blind, crossover, placebo-controlled study, we compared the behavioral and pharmacological effects of triazolam, meprobamate, and butabarbital in 14 recreational drug users. Placebo and three doses each of triazolam, meprobamate, and butabarbital were administered to each subject in a random order. Objective tests (motor performance, concentration) and subjective response questionnaires measured drug effects. Triazolam, meprobamate, and butabarbital showed comparable negative dose-response slopes on the objective measures. On the basis of these objective data, equivalent doses for the three compounds were determined to be as follows: 0.5 mg triazolam = 2,400 mg meprobamate = 400 mg butabarbital. Subjective effects data on equivalent doses show that butabarbital produced the highest peak score on Cole/ARCI Abuse Potential, ARCI Pentobarbital Chlorpromazine Alcohol Group (PCAG), and "drug strength" scales. Triazolam and butabarbital produced equivalent results on ARCI Morphine Benzedrine Group (MBG), Cole/ARCI Euphoria, and "drug liking" scales. Meprobamate was indistinguishable from placebo on euphoria and abuse potential scales. Behavioral economics analysis indicated a price crossover point two times higher for butabarbital (400 mg) than for any other drug condition. These data indicate a comparative abuse liability of butabarbital > triazolam > or = meprobamate, suggesting that the prescribing restrictions on benzodiazepines had little net benefit on abuse risk in the population and may have increased the risk of overdose morbidity and mortality.

An adult female ingested a considerable quantity of carisoprodol/acetaminophen tablets, which are not commercially available in Japan, in an attempt to commit suicide. Generally, because of lack of the appreciable ultraviolet absorbance or fluorescence, carisoprodol and its major metabolite meprobamate are determined by gas chromatography or gas chromatography-mass spectrometry. Complicated derivatization is, however, necessary to that methodology. Thus, we investigated the derivatization-free, highly sensitive, and simultaneous determination of carisoprodol, meprobamate, and acetaminophen by means of liquid chromatography-mass spectrometry (LC-MS) with positive electrospray ionization. A semi-micro ODS column was used. Ammonium acetate solution (10mM) and acetonitrile were used as mobile phase at a flow rate of 150 microL/min using gradient elution. MS parameters were as follows: capillary voltage, 3.5 kV; cone voltage, +30 V; extractor voltage, 5 kV; and ion source temperature, 100 degrees C. Urine samples pretreated by Oasis HLB cartridge, or plasma samples deproteinized by adding ice-cold acetonitrile were analyzed by LC-MS. The limits of quantitation for each compound were as follows: 0.50 ng/mL for carisoprodol; 10 ng/mL for acetaminophen; and 1.0 ng/mL for meprobamate. In the present case, carisoprodol and acetaminophen were the only drugs detected. Meprobamate was also found as the metabolite of carisoprodol in both urine and plasma. The plasma levels of carisoprodol, acetaminophen, and meprobamate on arrival were 29.5, 245, and 46.7 microg/mL, respectively. These levels were extremely high compared with therapeutic plasma concentrations. Despite the high plasma concentrations of these drugs, which correspond to fatal levels, the patient survived.

We describe a simple method for the urinary identification and blood quantitation of meprobamate suitable for any toxicological laboratory. After urinary screening using GC-MS technology, quantitation is performed by GC-MS in the selected-ion monitoring mode. Isolation of the drug is achieved by solid phase extraction on a C-18 cartridge. A specific elution is obtained by three volumes of acetone:triethylamine (99:1 v/v). Lidocaine is used as internal standard. RSDs (%) of the within-day and between-day precision studies are always less than 7.2 on the entire range of calibration. Linearity is inspected using an analysis of variance ANOVA. Homogeneity of the variances is tested using Hartley's test. Weighted linear regression is then computed. Limits of detection and quantification are given by an analysis of the blanks. The present method was applied in our laboratory over a period of 1 year. Meprobamate appeared as a drug which still has a significant frequency (5.5%) and is the most frequently involved in fatal pharmaceutical overdoses (15.3%). Post mortem concentrations ranged from 41 to 397 mg/l (mean = 182) and are compared to those of the literature.

We have investigated the efficacy of a pumpless hemoperfusion technique, continuous arteriovenous hemoperfusion (CAVHP) in 3 cases of acute intoxications with meprobamate, theophylline and phenobarbital. Dramatic responses were noted in both hemodynamic unstable and comatous patients. With this technique, a blood flow of 120 cm3/min could be achieved in severe hypotension. Moreover, with the restoration of blood pressure, blood flow increased to 150-400 cm3/min. Our preliminary experience has shown that CAVHP allows an exceptionally high solute elimination. Hemoperfusion clearances of meprobamate, phenobarbital and theophylline were 198 +/- 5.6 cm3/min, 290.25 +/- 25.33 cm3/min and 192.79 +/- 55 cm3/min, respectively. Our present results suggest that CAVHP is a simple, safe, effective and less costly alterative of conventional hemoperfusion.

A sensitive and specific quantitative assay for the determination of meprobamate in human fluids and hair is described. Meprobamate and an internal standard, vinylbarbital, are isolated by acid extraction and methylated by derivatization. The final extract is separated on a 12-m capillary column HP-1 and drugs are detected by selected ion monitoring at m/z 162 and m/z 182 for meprobamate and the internal standard, respectively. Applications in forensic science, particularly for hair analysis, are presented.

A simplified and rapid gas chromatographic method has been developed for the determination of meprobamate in human plasma. The procedure includes a single-step extraction of alkalinized sample with chloroform, and chromatography on a non-polar fused-silica capillary column with flame ionization detection. The method is accurate (97.7 +/- 5.7% at 20 mg/l) and precise (maximum coefficient of variation of 9.5%). It provides an alternative to existing methods and is particularly suitable for toxicological studies.

A patient with severe meprobamate poisoning presented within 4 h after suicidal ingestion of an unknown amount of the drug. The patient was unconscious, unresponsive, and hypotensive. Continuous arteriovenous hemoperfusion with coated activated charcoal resulted in a clearance of 198.8 +/- 15.6 mL/min with an extraction ratio of 0.66 +/- 0.05 (n = 3). There was almost complete elimination of the drug from the blood by 16 h. Continuous arteriovenous hemoperfusion, which can be performed in areas where dialysis facilities are not available, may be an effective adjunct to the treatment of acute meprobamate intoxication, particularly in patients with profound hypotension.

This gas chromatographic technique of determining meprobamate is based on a solid-phase extraction permitting a time reduction of the analysis and improving sensitivity. Quantification is realized on 500 microliters of plasma. The method uses etidocaine as internal standard and does not require derivatization. Thus it is simple, rapid, sensitive and applicable in forensic and clinical toxicological laboratories.

Effect of long-term ethanol administration on brain meprobamate concentration (BrMC) was investigated using rats. In ethanol-non-pretreated rats, the average ratio of the maximum BrMC (BrMCmax) to the maximum blood meprobamate concentration (BMCmax) was 0.75 when 25 mg/kg meprobamate were intraperitoneally administered to rats singly or together with ethanol (2 g/kg or 4 g/kg). By a pretreatment of the animals with ethanol at the daily dose of 0.4 g or 0.6 g for 25 days, the average ratio of BrMCmax to BMCmax was 0.91 when the same dose of meprobamate were given into the abdominal cavity. It was considered that by long-term ethanol administration the permeability of blood-brain barrier to meprobamate might be accelerated, resulting in an increase in BrMC.

Three cases involving overdoses of carisoprodol are presented. Concentrations of carisoprodol and its major metabolite meprobamate, were determined in urine, vitreous humor, heart, and femoral blood. All drugs were quantified by gas chromatography/mass spectrometry (GC/MS).

This paper describes the detection limit for 23 drugs and chemicals in the blood by means of a screening method that uses a gas chromatographic system equipped with a wide-bore capillary column and a nitrogen phosphorus detector. The detection limit by this method was determined as being 1 mm of peak height at the detector's range of 100 and 8 of attenuation. Using this scale, the absolute detection limit was in the range of 1 pg for malathion and sumithion to 1 ng for meprobamate. The detection limit of drugs and chemicals in the blood was 5 ng/ml for sumithion to 8 micrograms/ml for meprobamate. Therefore, this screening method is able to detect the presence of drugs even a therapeutic-level dosages, with the exception of compounds such as haloperidol, which have extremely low therapeutic dosage levels.

A case of meprobamate overdosage successfully treated with hemodialysis is described. The patient was admitted 4 hours after an overdosage of meprobamate (30-40 g) deeply unconscious, hypotensive, in respiratory failure and with a serum meprobamate level of 50 mg/100 ml. Hemodialysis was instituted using a Gambro parallel flow dialyzer and a portable re-circulating dialyzate delivery system (Redy, CCi Life Systems). Meprobamate removal with hemodialysis was 672+/-167 mg/hr with a corresponding clearance of 61.97+/-9.9 ml/min. Drug removal with forced diuresis was 177+/-23.4 mg/hr. Metabolic degradation of the drug was approximately 482 mg/hr with a plasma disappearance rate of 5.2%/hr. No drug could be detected in the dialyzate fluid after its passage through the Redy re-circulating dialyzate system. Because of the rapidity of metabolic degradation of meprobamate, we feel that hemodialysis should be reserved for severe clinical intoxication and either compromised normal excretory routes or progressive clinical deterioration.

A method is reported for separating drugs from serum lipids on special thin layer chromatographic media with insertable sample application discs, using a double-development, single dimensional technique. Drugs whose detection normally was precluded by lipid were detected at therapeutic levels using the new procedure.

The morphological and functional alterations of the smooth endoplasmic reticulum of the liver cell related to biliary stasis have brought attention to drug biotransformation during cholestasis. The metabolism of meprobamate, pentobarbital and tolbutamide was assessed in subjects with intrahepatic recurrent cholestasis (3), cholestatic hepatitis (6), extrahepatic biliary obstruction (7) and normal controls (16). In the patients with recurrent intrahepatic cholestasis no differences in drug metabolism were noted as compared to the control group. In cholestatic hepatitis the plasma half-lives of meprobamate (828 +/- 422 min.) and pentobarbital (39+-65) were significantly longer than in in controls (444 +/- 37 and 25.4 +/- 1.1 respectively). Tolbutamide plasma half-life appeared unchanged. The most striking variations were observed in the patients with extrahepatic biliary obstruction. In such cases while meprobamate half-life was unchanged, pentobarbital half-life was significantly prolonged (31.2 +/- 2.5) and the in vitro metabolism of the drug, using liver preparations, was decreased to less than 50% of the control value. In contrast the metabolism of tolbutamide was accelerated as evidenced by a significant decrease of plasma half-life (165 +/- 48 min. versus 384 +/- 76 of the controls) and an enhanced urinary excretion of the drug's metabolites. However the metabolism of tolbutamide in vitro did not show any difference between normal and cholestatic liver. Whatever the mechanism of the peculiar behaviour of tolbutamide in extrahepatic biliary obstruction it seems to be related to the increased bile dalt concentration during cholestasis. In fact the low values of plasma half-life increase significantly either relieving the biliary obstruction or producing a bile salt depletion with cholestyramine. Preliminary results in vitro suggest the bile salt could displace tolbutamide from albumin binding thus increasing the amount of free drug available for biotransformation by the liver. In conclusion cholestasis may affect drug metabolism depending on the degree of biliary stasis, liver cell injury and the type of drug tested. The mechanism could be that of an impaired biotransformation in the smooth endoplasmic reticulum or could involve extrahepatic factors.

A hemoperfusion system has been developed which makes use of activated carbon encapsulated with cellulose acetate. Studies have revealed that there are no stagnant flow regions in the column, there is minimal particle release and the coating is 30 A thick. The relationships between pore size, pore volume and surface area have been examined. Twenty-five patients in grade IV coma have been treated with the column for treatment of drug overdose or agricultural chemical poisoning; the clinical course of one meprobamate-poisoned patient is described in detail.

The absorption and elimination of alcohol and meprobamate from the blood during Experiments IV (E-IV) and V (E-V) of Carpenter et al. [J. Stud. Alc., Suppl. No. 7, pp. 54-139, 1975] were studied by means of mathematical models representing the relation between doses, concentration in the blood and time elapsing since drug ingestion. The blood concentrations of samples taken 2 and 5.5 hr after beginning to drink in E-IV and 1, 1.5, 2, 2.5, 3.5 and 4.5 hr in E-V were analyzed. The presence of meprobamate did not affect blood alcohol concentration (BAC) in either experiment. At 2 hr the mean BACS after 0.25, 0.50, 0.75 and 1.00 g of alcohol per kg were 6.8, 20.9, 37.7 and 53.7 mg per 100 ml in E-IV; 5.0, 34.1, 42.0 and 72.0 mg per 100 ml in E-V; and 8.1, 32.6, 41.3 and 71.3 mg per 100 ml when calculated by regression from E-V data. The calculated elimination rate of the 2 highest doses of alcohol in E-IV was 6.0 and 7.1 mg per 100 ml per hr; in E-V the mean calculated rates after 0.25-0.75 and after 1.00 g of alcohol per kg were 6.6 and 11.0 mg per 100 ml per hr. The blood meprobamate concentrations (BMC) in E-IV were not affected by alcohol. In E-V, 2.5 and 5.5 hr after meprobamate administration, the combination of 28 mg of meprobamate per kg and 0.75 g of alcohol per kg resulted in significantly lower BMC (7.83 and 12.63 mug per 100 ml) than after same dose of meprobamate with the other doses of alcohol (14.23 and 20.02 mug per 100 ml). The differences between these results and the findings of Carpenter et al. are discussed.

Some physicochemical treatments of biological samples, before being injected into a liquid chromatograph, are discussed. The advantages of dilution, liquid and solid extraction are compared referring mainly to unpublished results. Assays of antiepileptic drugs, caffeine, theophylline, tricyclic antidepressants, valproic acid, and meprobamate are used to demonstrate the importance of sample handlings in toxicological analyses in which reversed phase high performance liquid chromatographies are applied.

When rabbits were administered different amounts of ethanol during 25 and 50 days, the elimination of meprobamate from blood was not accelerated at daily ethanol dose of 0.4g/kg. The elimination was accelerated a little at daily ethanol dose of 0.8g/kg and markedly accelerated at the dose of 1.6g/kg. However, it was not accelerated furthermore at the dose of 2.4g/kg. Thus, accelerative effect of long-term ethanol administration on meprobamate metabolism may be greatly related to ethanol dosage and it is considered that the accelerative effects reach maximum at blood ethanol concentrations more than 1mg/ml. Also, elimination of meprobamate from brain in rats was fairly accelerated by long-term ethanol administration at the daily dose of 0.4g.

Arterial-venous plasma concentration differences of meprobamate were studied on admission of acute overdose in man. The patients were divided in two groups. In the control group (n = 25) two successive blood samples were collected from the same vessel. In the study group (n = 35) femoral arterial and venous blood samples were collected simultaneously. In the control group the differences were not significant. In the study group the differences were statistically significant (P less than 0.01). The present study suggests that the origin of blood samples should be stated for toxicological studies and that the toxicokinetics may be more complex than those recognized previously.

In the simultaneous administration of meprobamate and ethanol to rabbits, the blood meprobamate concentration (BMC) increased greatly when the maximum blood ethanol concentration (BECmax) exceeded 1.0 mg/ml. Thus, we subjected the rabbits to continuous infusion of ethanol so as to make the blood ethanol concentration (BEC) constant and administered meprobamate by intravenous injection. Elimination of meprobamate became slow at about the BEC of 0.5 mg/ml and the degree reached almost maximum around the BEC of 1.0 mg/ml. The elimination rate did not change any more even when the BEC was raised higher. In the study conducted to elucidate the relationship between the BMC and brain meprobamate concentration (BrMC) using rats, it was found that meprobamate would show similar movements and its level would rise extremely by an acute administration of ethanol. It was indicated that the effect of ethanol on reinforcement of meprobamate activity would appear strongly by potentiation effect.

Perfusion of the blood of a patient with toxic levels of meprobamate through an activated charcoal cartridge resulted in efficient early clearance of the drug, then a decline in extraction. Perfusion through a resin column resulted in total drug extraction without a decline in clearance over four hours. Both procedures were stable with minimal disturbance in hematological values or blood chemistries. This is the first report of in vivo hemoperfusion over resin for meprobamate poisoning. The efficacy and safety of the procedure need emphasis.

A 36-year-old female was treated successfully by hemoperfusion over Amberlite XAD-4 resin after ingestion of 40 gm of meprobamate. Hemoperfusion was started five hours after the ingestion. At that time the patient was in deep coma. The patient was treated by hemoperfusion for five hours, at the end of which time she was awake. Meprobamate clearance over the resin was about 290 mg/min. There were no bleeding complications. It is concluded that hemoperfusion over amberlite XAD-4 resin is a highly effective method in the treatment of severe cases of meprobamate intoxication.

Five experiments were conducted to study the effects of alcohol and meprobamate, administered singly and in combination, at doses up to 1.20 g of alcohol per kg of body weight and up to 30 mg of meprobamate per kg. Most of the 158 men were of college age (range, 21-49). In all experiments it appeared to the subjects that both drugs were administered, alcohol as a 25% solution in orange juice and meprobamate as 10 tablets. One hour after the men took the meprobamate they had 1 hr to drink the beverage. Before and at 1/2 hr intervals after administration of the drugs blood samples were taken and behavioral response measured by means of a visual-motor coordination tracking task (Stressalyzer). An experimental session lasted 6 hr. In Experiment I (E-I) each of 12 men was tested on 2 days, after 0, 1.00 or 1.20 g of alcohol per kg and 0 or 25 mg of meprobamate per kg. In Experiment II (E-II) 56 men were tested (8 per group) after 0, 5, 10, 15, 20, 25 or 30 mg of meprobamate per kg and alcohol placebo. In Experiment III (E-III) 40 men were tested (8 per group) after 0, 0.25, 0.50, 0.75, or 1.00 g of alcohol per kg and meprobamate placebo. In Experiment IV (E-IV) 25 men (5 per group) received meprobamate 3 times a day (total daily dosage, 0, 7, 14, 21 or 28 mg per kg) for 12 days. On days 8 to 12 all subjects drank alcohol, as in E-III. In Experiment V (E-V) 25 subjects (5 per group) were tested on 5 days, drinking each day the same doses of alcohol as in E-III and all received the same doses of meprobamate as in E-IV.