1.1. Carisoprodol is an orally active centrally acting muscle relaxant that was used clinically in the UK to treat painful muscle spasm.
1.2. In 2007 the European Medicines Agency recommended that Member States (including the UK at that time) suspend marketing authorisation for carisoprodol [EMA 2007]. After review, it was concluded that the benefits of medicines containing carisoprodol no longer outweighed the risks from its use. These risks include an increased likelihood of abuse and addiction as well as intoxication and psychomotor impairment. It was considered that there were safer alternatives for the treatment of acute musculoskeletal disorders where a muscle relaxant was needed. As a result, in the UK the marketing authorisations for carisoprodol were withdrawn in 2008 [MHRA, 2008].
1.3. Carisoprodol is still available as a prescription medicine in a number of countries including the USA [WHO 2023]. In 2019, more than 800,000 prescriptions for carisoprodol were issued in the USA [ClinCalc 2020].
1.4. The major metabolite of carisoprodol, meprobamate, was itself used clinically for short-term treatment of anxiety or painful muscle spasm. In 2012, the European Medicines Agency recommended the suspension of marketing authorisations for medicines containing meprobamate. In the UK the license for meprobamate production was cancelled in 2016. [MHRA 2016].
1.5. Carisoprodol is used non medically to produce feelings of relaxation, giddiness, and drowsiness. It is typically consumed orally, but when taken by insufflation (snorted), a more intense euphoria may be experienced which is likely due to more rapid absorption of the drug. It may be combined with other drugs such as opioids and benzodiazepines resulting in an enhanced ‘high’ but also with an increased likelihood of overdose [Horsfall 2017].
1.6. Carisoprodol induced relaxation and euphoria are generally short-lived due to fast metabolism to meprobamate and to other metabolites. The sedative effects of carisoprodol are longer lasting and are generally attributed to meprobamate which persists in the body for much longer than carisoprodol...