CYP2C19 genetics in fatal carisoprodol intoxications.

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.

Postmortem carisoprodol and meprobamate concentrations in blood and liver: lack of significant redistribution.

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.

Behavioral and toxicological effects of propofol.

There is increasing concern about abuse of propofol, a widely-used surgical anesthetic and sedative that is currently not a controlled substance. The purpose of this study was to establish a rat model of the psychoactive effect of subanesthetic doses of propofol that could be useful for confirming abuse liability and for studying mechanisms of propofol abuse. Sprague-Dawley rats were trained to discriminate propofol (10 mg/kg, intraperitoneally) from vehicle (2% methylcellulose). Carisoprodol (100 mg/kg), chlordiazepoxide (10 mg/kg), and dizocilpine (0.1 mg/kg) were tested for substitution for the discriminative-stimulus effects of propofol (10 mg/kg), whereas pentylenetetrazol (10 mg/kg) was tested for antagonism of the discriminative-stimulus effects. Propofol (10 mg/kg) was tested for substitution in rats trained to discriminate carisoprodol from vehicle. Carisoprodol produced 59% propofol-appropriate responding, chlordiazepoxide produced 65% propofol-appropriate responding, and dizocilpine produced 34% propofol-appropriate responding. Pentylenetetrazol decreased propofol-appropriate responding to 41%. Propofol produced 52% carisoprodol-appropriate responding. Mortality rate during training of propofol (10 mg/kg) was 38%. Postmortem examination revealed cardiovascular abnormalities similar to those observed in propofol-infusion syndrome in humans. The results demonstrate that propofol can be trained as a discriminative stimulus. Its discriminative-stimulus effects were more similar to compounds promoting γ-aminobutyric acid-A receptor activity than to a compound inhibiting N-methyl-d-aspartate receptor activity. As propofol has discriminative-stimulus effects similar to known drugs of abuse, and occasions a high-mortality rate, its potential for continued abuse is of particular concern.

Ingestions of hydrocodone, carisoprodol, and alprazolam in combination reported to Texas poison centers.

The combination of hydrocodone, carisoprodol, and alprazolam is subject to abuse. Ingestions of this drug combination reported to Texas poison centers during 1998-2009 were identified (totaling 1,295 cases) and the distribution of ingestions by selected factors was determined. The number of cases increased from 0 in 1998 to 200 in 2007, and then decreased to 132 in 2009. The counties in eastern and southeastern Texas accounted for 80.9% of the cases. Of the patients, 57.3% were women and 94.6% were age 20 or older. Suspected attempted suicide accounted for 59.3% of the cases and intentional misuse or abuse for 27.3%.

The effect of scheduling and withdrawal of carisoprodol on prevalence of intoxications with the drug.

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.

A multi-drug intoxication fatality involving Xyrem (GHB).

Gamma-hydroxybutyrate (GHB) is best known as a recreational depressant drug, whose use has also been implicated in drug facilitated sexual assault cases. It is also available as a therapeutic agent (Xyrem) used for the treatment of daytime sleepiness or cataplexy associated with narcolepsy. This is a report of a case of a 53-year-old woman undergoing treatment with Xyrem for narcolepsy. The decedent was also prescribed tramadol, gabapentin, cetirizine, modafinil, carisoprodol, and Xyrem. Toxicological analysis of the blood revealed GHB 165.6 mg/L, and 90.7 mg/L in the urine. Blood GHB concentrations in the range 156-260 mg/L have been reported to induce moderately sound sleep. The combined use of central nervous system depressant drugs, together with her problematic sleep apnea, and snoring (both contraindications for GHB use) were determined to have caused this subject's death. The manner of death was determined to be accidental.

Acute intoxications with carisoprodol.

Carisoprodol is a drug frequently prescribed for lower back pain. Several case reports on the toxic potential have been published. Larger autopsy materials have supported the high toxicity of the drug, but have also shown that carisoprodol most often appears in mixed intoxications. The present study reports on contacts concerning possible intoxications with carisoprodol to the Norwegian Poisons Information Department. From 1992 to 2003, the number of contacts concerning carisoprodol rose heavily, also when adjusting for increasing total number of contacts. There was a relationship between the whole sales figure of carisoprodol and the number of contacts. Of the cases classified as "serious intoxications", carisoprodol was the second most frequent drug, only surpassed by acetaminophen (paracetamol). Despite the potential weaknesses of the present material, this study gave an additional indication of a high toxicity of carisoprodol.

Carisoprodol intoxications: a retrospective study of forensic autopsy material from 1992-2003.

Carisoprodol is commonly prescribed as a centrally acting muscle relaxant, but it is also subject to abuse. The literature describing fatal intoxications with the drug is limited to a relatively small number of cases, and there are inconsistencies with regard to which concentration levels that are toxic. We therefore investigated all forensic autopsies at the Norwegian Institute of Public Health during the period 1992-2003 where carisoprodol was detected. The median concentrations of carisoprodol in intoxication with carisoprodol only or with only minor other analytical findings was 36 mg/l (range 8-65 mg/l; n=5). In the rest of the intoxications, the relevance of carisoprodol relative to the other drugs detected was variable (n=93). When the number of intoxications with carisoprodol each year were divided by the number of defined daily doses (DDD) sold, a fatal toxicity index between 5.6 and 6.9 deaths/1 million DDD was obtained. The total number of cases where carisoprodol was detected increased during the period studied, which correlated to sales figures for the drug. We conclude that carisoprodol can be fatal in concentrations below those indicated in some of the previously published literature. There were, however, only a small number of cases where the cause of death can be attributed to use of carisoprodol alone.

Role of drug testing as an early warning programme: the experience of the Republic of Korea.

Drug testing plays an important role in the provision of information to health authorities on trends in drug abuse. In the Republic of Korea, the testing of urine and postmortem specimens has been used as part of a programme to monitor and control the abuse of non-controlled drugs, i.e., substances that were not originally included in the lists of controlled substances in that country. Zipeprol, dextromethorphan, carisoprodol and nalbuphine are examples of such drugs, which are widely used as medicines. Increasing levels of abuse of these drugs, including abuse that resulted in fatalities, were confirmed in the Republic of Korea by the results of drug testing. Based on the accumulated data from postmortem specimens, the health authorities in the Republic of Korea subsequently introduced controls on these drugs. A significant drop in fatalities related to the abuse of these non-controlled drugs underlined the importance of timely action for improving community health. In the context of drug testing, the analysis of non-controlled and new drugs always presents a scientific challenge, because specific analytical methods for testing for those drugs are not available. In the Republic of Korea, as part of the drug abuse warning programme, it was necessary to establish methods for the detection and quantification in biological fluids of all four non-controlled drugs and their metabolites in order to monitor the trends in drug abuse. The present paper puts forward epidemiological and clinical data on abuse and fatalities associated with zipeprol, dextromethorphan, carisoprodol and nalbuphine, as well as details of the analytical methods developed.

Simultaneous determination of carisoprodol and acetaminophen in an attempted suicide by liquid chromatography-mass spectrometry with positive electrospray ionization.

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.

Flumazenil reversal of carisoprodol (Soma) intoxication.

A 52-year-old woman presented with central nervous system depression and a Glasgow Coma Score of 9 secondary to ingestion of carisoprodol, a centrally acting muscle relaxant analgesic. After administration of i.v. flumazenil, the patient's neurologic status normalized and she required no further therapy. Carisoprodol and its active sedative-hypnotic metabolite, meprobamate, are gamma aminobutyric acid receptor indirect agonists with central nervous system chloride ion channel conduction effects similar to the benzodiazepines, thus making flumazenil a potentially useful antidote in toxic presentations.

Carisoprodol-induced myoclonic encephalopathy.

CASE REPORT: A 39-year-old man ingested 35 g carisoprodol. He developed agitation, tachycardia, myoclonus, and coma. The blood carisoprodol was 71 micrograms/mL; the meprobamate was 26 micrograms/mL. DISCUSSION: Carisoprodol overdose is thought to induce simple central nervous system depression. This case demonstrates a severe overdose with symptoms more consistent with myoclonic encephalopathy. A review of cases presenting to the San Francisco Division of the California Poison Control System during 1997 suggests that carisoprodol is more commonly associated with agitation and bizarre movement disorders than the current literature suggests. The pharmacology and potential mechanisms of toxicity are discussed. CONCLUSION: Agitation, hypertonia, and a myoclonic encephalopathy may be seen with significant carisoprodol intoxication.

A review of carisoprodol deaths in Jefferson County, Alabama.

BACKGROUND: Carisoprodol is a skeletal muscle relaxant with the potential for abuse. A carisoprodol overdose is rarely considered fatal. Nevertheless, we encountered carisoprodol in several cases, prompting review of our experience. METHODS: We did a retrospective study of cases examined at the Jefferson County Coroner/Medical Examiner Office from January 1, 1986, to October 31, 1997, reviewing investigative reports and autopsy findings. RESULTS: Carisoprodol was present in 24 cases. Seventeen decedents died of acute drug intoxication. Carisoprodol was never the sole drug detected at autopsy, nor was it ever the sole cause of death. Propoxyphene was a co-intoxicant in 8 of the 24 cases. CONCLUSIONS: Carisoprodol causes respiratory depression. Since the mechanism of death was respiratory depression in 82% of the decedents who died of acute intoxication, we consider that carisoprodol was probably responsible, in part, for those deaths. The simultaneous use of propoxyphene and carisoprodol seems to be especially dangerous.

Carbidopa-levodopa overdose.

A 57-year-old woman ingested 15 to 17 tablets of carbidopa-levodopa 10/100 tablets (carbidopa 150 mg and levodopa 1,500 mg) along with ibuprofen, carisoprodol, hydrocodone, and acetaminophen. The patient developed choreiform movements that persisted despite obtundation and attempts to extinguish them with naloxone, morphine, and diazepam. When the patient developed a rising level of creatine phosphokinase and myoglobinuria, she was treated with ventilatory support and pancuronium. She required paralysis for 60 hours, when her chorea resolved.

Carisoprodol concentrations from different anatomical sites: three overdose cases.

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).

Carisoprodol-related death in a child.

A child who ingested approximately 3500 mg of carisoprodol gradually deteriorated and died within 36 h. GC analysis of serum, urine, and gastric samples indicated that meprobamate was the principal metabolite of carisoprodol.