Is the frequency of carisoprodol withdrawal syndrome increasing?

Carisoprodol is a commonly used centrally acting muscle relaxant. A number of case reports have suggested that the drug may have abuse potential, presumably because it is metabolized to the anxiolytic drug, meprobamate, which is a controlled substance at the federal level. Two recent case reports described symptoms of withdrawal after the cessation of carisoprodol. We present two additional cases that support the concept of a withdrawal syndrome with this drug. Symptoms of carisoprodol withdrawal include anxiety, tremulousness, insomnia, jitteriness, muscle twitching, and hallucinations. These symptoms are most likely caused by withdrawal from the meprobamate that accumulates after large amounts of carisoprodol are ingested. Although carisoprodol is not a controlled substance at the federal level, clinicians should be aware of its significant potential for abuse.

The risk of traffic accidents after prescriptions of carisoprodol

OBJECTIVE

Carisoprodol, a drug used for acute lower back pain, may cause psychomotor impairment. We wanted to investigate if patients using carisoprodol had increased risk of being involved in a traffic accident.

METHODS

Data were retrieved from three population-based registries for the period April 2004-September 2005. The Norwegian Prescription Database contained individual information on all dispensed drugs at all pharmacies outside hospitals. The Norwegian Road Accident Registry contained information on all drivers involved in motor vehicle accidents with person injury. The Norwegian Central Population Registry was used to control for emigration or death. The accident incidence among carisoprodol exposed and unexposed subjects was compared by standardized incidence ratio.

RESULTS

Having a prescription for carisoprodol dispensed increased the standardized incidence ratio for being involved in an accident with person injury to 3.7 (95% CI 2.9-4.8) the first week after the date of dispensing. This was similar to diazepam (2.8; 2.2-3.6), but higher than for salbutamol (1.1; 0.6-1.8).

CONCLUSIONS

Patients receiving carisoprodol seem to have an increased risk of being involved in traffic accidents involving person injury. The study gives support to earlier work published on the impairing effects of carisoprodol.

Carisoprodol use and abuse in Norway: a pharmacoepidemiological study

AIM

Carisoprodol was developed to create a drug with less potential for abuse than meprobamate. However, case reports have established carisoprodol as a drug of abuse. This paper explores the extent of potential abuse of this drug in Norway.

METHODS

The Norwegian Prescription Database contains information on prescription drugs dispensed to individuals in Norway. Patients can be followed over time. High levels of carisoprodol use could indicate use for pleasurable effects or development of tolerance. Concomitant use of other potential drugs of abuse was also studied. We studied drug-seeking behaviour by looking at patients who received carisoprodol from many different pharmacies and doctors or from high-prescribing doctors. Carisoprodol was compared with a series of other medicinal drugs with or without known potential for abuse.

RESULTS

Some 53,889 Norwegian women (2.4%) and 29,824 men (1.3%) > or =18 years old received carisoprodol at least once in 2004. Prescribing of carisoprodol was skewed. As many as 32% of the patients received more than 15 defined daily doses (DDDs) of carisoprodol and >11,000 patients (15%) received > or =75 DDDs in 2004. High users of carisoprodol also received more benzodiazepines and opioids. Few patients used three or more doctors for prescriptions, but carisoprodol-abusing patients more often received their prescription from high-prescribing doctors.

CONCLUSIONS

Carisoprodol was widely used and the skewedness in use indicated that it is a potential drug of abuse. A large number of patients used more carisoprodol than recommended in the guidelines. The high level of use and abuse of carisoprodol should be of concern in Norway.

Carisoprodol intoxications and serotonergic features

The symptoms and signs of carisoprodol intoxications do not resemble those caused by its metabolite meprobamate. Meprobamate most probably produces its effects through the GABAergic neurotransmitter system. The signs and symptoms of carisoprodol intoxications, however, are not easily explained by interaction with this neurotransmitter system. In the present study, four cases of carisoprodol intoxications are presented with emphasis on the presence of serotonergic signs and symptoms. All four cases fulfilled three different sets of criteria for the diagnosis of serotonin syndrome. These findings could indicate that an increased serotonin level in the central nervous system could explain some of the symptoms and signs of carisoprodol intoxications. This may have implications for the clinical evaluation and treatment of such intoxications. Since few laboratories routinely screen for carisoprodol it is important to keep this drug in mind when encountering intoxications displaying serotonergic symptoms.

Carisoprodol Withdrawal Syndrome

A 43-year-old man with chronic back and shoulder pain was treated with hydrocodone. He began taking excessive amounts of the drug, so his physicians stopped prescribing it. The patient then obtained the muscle relaxant carisoprodol on his own from several sources. He was consuming up to 30 or more tablets/day (> or =10,500 mg/day) for several weeks, then abruptly stopped taking the drug. Within 48 hours he developed anxiety, tremors, muscle twitching, insomnia, auditory and visual hallucinations, and bizarre behavior. The symptoms intensified and peaked on the fourth day after carisoprodol cessation. The patient required brief treatment with olanzapine and tapering dosages of lorazepam while the symptoms gradually resolved. To our knowledge, this is the first documented case of a withdrawal syndrome with carisoprodol. The symptoms most likely resulted because of accumulation of meprobamate, the active metabolite of carisoprodol in humans. Clinicians prescribing carisoprodol should be aware of the possibility for abuse or addiction. Further, we recommend that carisoprodol be designated a controlled substance at the federal level.

Commonly used muscle relaxant therapies for acute low back pain: a review of carisoprodol, cyclobenzaprine hydrochloride, and metaxalone

BACKGROUND

Low back pain is a leading reason for primary care visits. Many treatment options are available, but some lack scientific support.

OBJECTIVE

The aim of this review was to discuss the etiology of low back pain and the relative risks and benefits of muscle relaxants commonly prescribed for the management of back pain.

METHODS

We searched Intercontinental Marketing Services data for January 2003 through January 2004 to determine the most commonly prescribed agents for the management of musculoskeletal pain. Carisoprodol, cyclobenzaprine hydrochloride, and metaxalone represented >45% of all such prescriptions. Cochrane Library, MEDLINE, and EMBASE databases were searched (time frame: 1960 through January 2004; search terms: back pain, carisoprodol, cyclobenzaprine, metaxalone, muscle relaxants, and pharmacotherapy) and reference lists of identified articles were hand-searched.

RESULTS

Three trials of carisoprodol (N = 197) were located in the Cochrane Library database. Two double-blind, randomized, placebo-controlled trials evaluating the safety and efficacy of cyclobenzaprine hydrochloride (N = 1405) were identified in the literature. Three double-blind, placebo-controlled trials were identified for metaxalone (N = 428) in 2 reports. The types of adverse events seen with these agents involved the central nervous system, including drowsiness/sedation, fatigue, and dizziness. However, the efficacy of cyclobenzaprine hydrochloride was shown to be independent of its sedative effects, which were dose related. The potential for abuse with carisoprodol is of growing concern.

CONCLUSIONS

Analgesic pain management for low back pain due to muscle spasm may be combined with a muscle relaxant. Cyclobenzaprine hydrochloride has the most recent and largest clinical trials demonstrating its benefit, but carisoprodol and metaxalone also appear to be effective. However, carisoprodol's usefulness is mitigated by its potential for abuse.

Impairment due to intake of carisoprodol

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.

Somatic dysfunction during carisoprodol cessation: evidence for a carisoprodol withdrawal syndrome

Carisoprodol is a commonly used skeletal muscle relaxant with potential for abuse because of its active metabolite, meprobamate, and several reports have suggested that patients abruptly stopping intake of carisoprodol may have a withdrawal syndrome. The authors studied changes in the occurrence of somatic dysfunctions in five patients during an 8-day period following discontinuation from large doses of carisoprodol. Results showed that the number of somatic dysfunctions changed significantly during the withdrawal period. Each patient had an increase in the number of somatic dysfunctions during the first 3 days after cessation of carisoprodol with return to at or near baseline by the eighth day. This was reflected statistically in a significant-within-subjects effect for time. Results of supplemental analyses revealed a significant component of the effect and a trend for the quadratic component to be significant. Increases in the number of somatic dysfunctions during carisoprodol discontinuation support the existence of a carisoprodol withdrawal syndrome.

WHO Expert Committee on Drug Dependence. Thirty-second report

This report presents the recommendations of a WHO Expert Committee responsible for reviewing information on dependence-producing drugs to assess the need for their international control. The first part of the report contains a general discussion of the new guidelines for the review of dependence-producing psychoactive substances and their implications for the scheduling of ephedrine and of the guidelines that were drafted to clarify the scope of control of stereoisomers. A summary follows of the Committee's evaluations of six substances (4-bromo-2,5-dimethoxyphenethylamine (2C-B), 4-methylthioamphetamine (4-MTA), gamma-hydroxybutyric acid (GHB), N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MDBD), diazepam and zolpidem), four of which (2C-B, 4-MTA, GHB and zolpidem) were recommended for international control. The report also discusses the substances that were pre-reviewed by the Committee, five of which (amfepramone, amineptine, buprenorphine, dronabinol and tramadol) were recommended for critical review at a future meeting.

[Centrally acting muscle relaxants and traffic hazards]

BACKGROUND

An increasing number of the centrally acting muscle relaxants were withdrawn from the Norwegian market during the 1988-98 period. The only drug in this group now marketed in Norway is carisoprodol. The National Institute of Forensic Toxicology in Norway analyses all blood samples from suspected drugged drivers. In later years there has been a marked increase in the number of blood samples testing positive for carisoprodol or meprobamate (the major metabolite).

MATERIAL AND METHODS

480 cases testing positive for central muscle relaxants in the years 1984-1998 were further studied.

RESULTS

Compared with blood samples positive primarily for benzodiazepines, there were more women in the group (39% vs. 15%), and fewer drugs and less alcohol were detected.

INTERPRETATION

The positive samples may indicate misuse or abuse due to the fact that high drug concentrations and concomitant use of benzodiazepines were frequent. This knowledge should have implications for doctors prescribing centrally acting muscle relaxants.

Carisoprodol, meprobamate, and driving impairment

This paper considers the pharmacology of the centrally acting muscle relaxant carisoprodol, and its metabolite meprobamate, which is also administered as an anxiolytic in its own right. Literature implicating these drugs in impaired driving is also reviewed. A series of 104 incidents in which these drugs were detected in the blood of drivers involved in accidents or arrested for impaired driving was considered, with respect to the analytical toxicology results, patterns of drug use in these subjects, the driving behaviors exhibited, and the symptoms observed in the drivers. Symptomatology and driving impairment were consistent with other CNS depressants, most notably alcohol. Reported driving behaviors included erratic lane travel, weaving, driving slowly, swerving, stopping in traffic, and hitting parked cars and other stationary objects. Drivers on contact by the police displayed poor balance and coordination, horizontal gaze nystagmus, bloodshot eyes, unsteadiness, slurred speech, slow responses, tendency to doze off or fall asleep, difficulty standing, walking or exiting their vehicles, and disorientation. Many of these cases had alcohol or other centrally acting drugs present also, making difficult the attribution of the documented impairment specifically to carisoprodol and meprobamate. In 21 cases, however, no other drugs were detected, and similar symptoms were present. Impairment appeared to be possible at any concentration of these two drugs; however, the most severe driving impairment and most overt symptoms of intoxication were noted when the combined concentration exceeded 10 mg/L, a level still within the normal therapeutic range.

Carisoprodol (soma): abuse potential and physician unawareness

Carisoprodol is a noncontrolled skeletal muscle relaxant whose active metabolite is meprobamate, a Schedule IV controlled substance. Although several case reports have shown that carisoprodol has abuse potential, it continues to be widely prescribed. The usage patterns of 40 patients who had taken carisoprodol for three or more months (20 of whom had no history of substance abuse and 20 of whom carried a diagnosis of substance abuse or dependence) were reviewed and compared and a survey was conducted to assess physician awareness of the abuse potential of the drug. Findings showed that some patients using carisoprodol for over three months may abuse the medication, especially those individuals with a history of substance abuse. A significant percentage of the physician population is unaware of the potential of carisoprodol for abuse and of its metabolism to meprobamate, a controlled substance. Physicians should exercise caution when prescribing carisoprodol, especially if the patient has a history of substance abuse.

Carisoprodol: a drug of continuing abuse

Carisoprodol (Soma) is a noncontrolled, skeletal-muscle relaxant whose active metabolite is meprobamate. Despite previous indications that the drug may be abused, it continues to be widely prescribed for musculoskeletal conditions involving muscle spasm. Presented here are three cases demonstrating patterns of carisoprodol abuse not previously reported. Carisoprodol usage should be limited to short-term treatment. Patients for whom carisoprodol is prescribed are at risk for meprobamate dependence.

Carisoprodol (Soma): a new and cautious perspective on an old agent

Carisoprodol (Soma, others) is a commonly prescribed, noncontrolled, skeletal muscle relaxant whose active metabolite is meprobamate. Patients for whom carisoprodol is prescribed are at risk for meprobamate dependence; several such cases have been reported. Toxicity and withdrawal associated with the use of meprobamate is high and has led to abandonment of this agent in clinical practice. Because carisoprodol possesses the same risks it should be avoided when possible, and it should be given schedule IV controlled substance status.