Background: An increasing number of the centrally acting muscle relaxants were withdrawn from the Norwegian market during the 1988-98 period.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.