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 In Norway, carisoprodol was therefore reclassified to the highest scheduling level from 1 August 2007 and withdrawn from the market on 1 May 2008.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.