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These combinations are considered extremely harmful and should always be avoided. Reactions to these drugs taken in combination are highly unpredictable and have a potential to cause death.
These combinations are not usually physically harmful, but may produce undesirable effects, such as physical discomfort or overstimulation. Extreme use may cause physical health issues. Synergistic effects may be unpredictable. Care should be taken when choosing to use this combination.
Carisoprodol has significant psychological addiction potential with documented abuse cases even when used without other drugs possessing abuse potential. Compulsive redosing is a recognized effect, and users frequently escalate to very high daily doses. Its potent anxiolytic effects and euphoria are implicated in drug-seeking behavior. Psychological dependence is more common in those who use it non-medically or have a history of substance use.
Physical dependence of the barbiturate type develops following prolonged use. Withdrawal can be life-threatening, particularly in high-dose users or those who stop abruptly, and may require hospitalization. Severe withdrawal can mimic alcohol withdrawal including potentially lethal status epilepticus. The accumulation of meprobamate, which has a longer half-life, contributes to withdrawal severity.
Using over 12 grams acutely is considered potentially life-threatening in adults. A fatal case occurred in a 4-year-old child with 3.5 grams. Fatal overdoses are more commonly associated with combinations involving opioids, benzodiazepines, or alcohol. Fatal blood concentrations have been reported ranging from approximately 8-40 ug/mL, often in polydrug scenarios.
| Species | Route | Value |
|---|---|---|
| rat | IV | 450 mg/kg |
| rat | IP | 450 mg/kg |
| rat | oral | 1320 mg/kg |
| mouse | IV | 165 mg/kg |
| mouse | IP | 980 mg/kg |
| mouse | oral | 2340 mg/kg |
| rabbit | IV | 124 mg/kg |
Overdose causes CNS depression ranging from lethargy to deep coma; chronic use and withdrawal can result in prolonged cognitive changes including memory impairment, reduced IQ, increased anxiety and depression, and in some cases these effects persist for months or years after discontinuation.
Respiratory depression occurs primarily in overdose situations and is significantly more dangerous when carisoprodol is combined with other CNS depressants; mechanical ventilation may be required in severe cases.
Psychotic symptoms occur primarily during withdrawal rather than acute intoxication. Approximately 20% of withdrawal cases feature hallucinations (mainly visual and auditory) or other psychotic symptoms. Case reports document patients experiencing vivid hallucinations of insects, animals, people, and voices indistinguishable from reality, along with paranoid ideation. Symptoms typically peak 3-5 days after cessation and may last up to 8-9 days.
Unlike benzodiazepines, carisoprodol increases rather than decreases seizure risk. Seizures can occur both in overdose and during withdrawal. Withdrawal seizures can progress to potentially lethal status epilepticus, similar to alcohol withdrawal. Drugs that lower seizure threshold should be avoided during withdrawal. Deaths have been reported in association with carisoprodol-related seizures.
Frank M. Berger at Wallace Laboratories (later Carter-Wallace) synthesized carisoprodol in 1956. Berger had also been part of the team responsible for creating meprobamate, which had become a widely used pharmaceutical during the 1950s. The development of carisoprodol arose from ongoing efforts to…
Removed from the Australian Register of Therapeutic Goods. Access is still possible through the Special Access Scheme for individual patient needs.
The European Medicines Agency recommended member states suspend marketing authorization in 2008 due to concerns about dependence and insufficient benefit-risk profile for acute back pain treatment.
Classified as a prescription medicine under Anlage 1 of the Arzneimittelverschreibungsverordnung (AMVV). Available only with a valid medical prescription.
Sold over-the-counter, though typically in lower doses than those available in the United States. Commonly advertised in border cities.
Reports indicate carisoprodol may be available without prescription, though this has not been officially confirmed.
As of 2005, reported to be available without prescription in combination formulations with phenylbutazone or paracetamol. Status may have changed since then.
As of April 14, 2025, carisoprodol was removed from the Prescription Drug List and reclassified as a Schedule V Controlled Substance. No pharmaceutical forms are currently marketed in Canada.
Carisoprodol is no longer available in Finland, including as a prescription medication. Previously marketed as Somadril.
Taken off the market in September 2013 due to concerns about diversion, dependence, and adverse effects.
Removed from the market in May 2008 following reports demonstrating addictive potential as a prodrug of meprobamate and as a potentiator of opioid medications including hydrocodone, oxycodone, and codeine.
Taken off the market in November 2007 due to problems with dependence and side effects. The Swedish pharmaceutical regulatory agency determined that alternative medications offered comparable or better efficacy without the associated risks.
Placed on Schedule IV of the Controlled Substances Act by DEA ruling in December 2011, effective January 2012. Classification followed rising rates of abuse and diversion. Requires a valid prescription for legal possession; unauthorized possession or distribution is a federal offense.
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