Carisoprodol is a carbamate ester that acts as a central nervous depressant. It can be used as a sedative and skeletal muscle relaxant in order to treat pain from acute injuries and musculoskeletal conditions.1 Its mechanism of action is not fully understood, but it produces the same effects as barbiturate receptor ligands. It is believed that carisoprodol’s sedative effects are partially mediated through meprobamate, one of its metabolites. Both of these drugs activate and allosterically modulate GABA-A receptor proteins.2 Unlike other muscle relaxants, which act directly on skeletal muscles, carisoprodol acts on the central nervous system by interrupting neuronal communication in the reticular formation and the spinal cord, thereby reducing pain perception.3
Common side effects of carisoprodol include:
Patients should contact a doctor immediately if they experience serious side effects, such as:
Patients should seek emergency assistance if they experience an allergic reaction to carisoprodol, which may be characterized by hives, difficulty breathing, or swelling of the lips, tongue, and throat.7
Patients who are allergic to meprobamate, tybamate, or mebutamate should not take carisoprodol. Patients who have a history of acute intermittent porphyria, kidney disease, liver disease, seizure, or drug abuse should talk to a doctor before starting carisoprodol.
The sedative effects of carisoprodol may be magnified by other central nervous system depressant drugs, such as benzodiazepines, opioids, and tricyclic antidepressants. Meprobamate, a metabolite of carisoprodol, may also enhance the drug’s effects. The enzyme CYP2C19 metabolizes carisoprodol in the liver to produce meprobamate and other metabolites, so the ratio of active carisoprodol to active meprobamate will change in the presence of drugs that induce or inhibit CYP2C19.8 Inducers include aminoglutethimide, barbiturates, carbamazepine, phenytoin, primidone, rifampin, and St. John’s Wort. Inhibitors include cimetidine, clopidogrel, delavirdine, efavirenz, esomeprazole, felbamate, fluconazole, fluoxetine, moclobemide, modafinil, omeprazole, oxcarbazepine, ticlopidine, and voriconazole.9 Patients are also advised against drinking alcohol alongside carisoprodol, as it may increase the drug’s sedative effects.
Carisoprodol was developed in New Jersey in the 1950’s. It was intended to be a safer, less addictive, and more effective alternative to meprobamate. It was approved for use as a muscle relaxant by the FDA in 1959 and was marketed as “Soma.” Carisoprodol is still one of the most popular skeletal muscle relaxants in the United States today, accounting for more than one-fifth of all prescriptions.10
In recent years, carisoprodol has become an increasingly popular recreational drug because of its sedative effects. Users describe a “soma coma” that is characterized by drowsiness and pain relief. Carisoprodol is commonly used in combination with codeine, or with hydrocodone (Vicodin) and alprazolam (Xanex) in what is known as a “Houston Cocktail” or “Holy Trinity.” In 2009, carisoprodol use was responsible for 30,000 emergency room visits in the United States.11 Users build up tolerance to carisoprodol relatively quickly, and abuse often leads to addiction.
Due to the increasing frequency of abuse, governments around the world have placed stricter regulations on the use of carisoprodol as a prescription drug. It has been taken off the market in Sweden, Norway, and Indonesia, and the European Union has recommended that member states suspend authorization of the drug for the treatment of lower back pain. In January 2012, the federal government of the Unites States classified carisoprodol as a schedule IV controlled substance. It has also been classified as a controlled substance by several states.[“Carisoprodol: update on abuse potential and legal status,” November 2012, http://www.ncbi.nlm.nih.gov/pubmed/23128807]
Because of the potential for abuse, recent research has focused primarily on carisoprodol’s toxicity and its effects when used in combination with other drugs. Scientists also continue to explore the drug’s mechanism of action in the hopes of better understanding its muscle relaxant and sedative effects.
Many compound pharmacists prefer Cyclobenzaprine or Orphenadrine Citrate for treating short-term musculoskeletal pain because they are less addictive than carisoprodol. Baclofen is another muscle relaxant that may be safer for long-term use. Please find more information about our Bulk APIs here.