Fatal unintentional intoxications with tramadol during 1995-2005

Tramadol is an extensively used centrally acting analgesic and is considered a safe drug devoid of many serious adverse effects of traditional opioids. However, recently, toxicity and an abuse potential of tramadol have been reported. This study examined fatal unintentional tramadol intoxications among Swedish forensic autopsy cases between 1995 and 2005. All fatal intoxications were selected, in which toxic concentrations of tramadol (>1 microg/g femoral blood) had been detected, and where the forensic pathologist considered the intoxication unintentional and the fatal outcome at least partly explained by tramadol. Toxicology analyses, police reports, autopsy protocols and medical records were scrutinized. A total of 17 cases (eleven men and six women) of fatal unintentional tramadol intoxications were identified. For these cases the median age was 44 years (range 18-78 years) and the median tramadol concentration was 2.0 microg/g (range 1.1-12.0 microg/g). Other pharmaceutical substances, illicit drugs or ethanol were detected in addition to tramadol in all of these cases. In fact, intoxication with multiple drugs was considered the cause of death in 10 (59%) cases. However, in seven cases tramadol was the only substance present in toxic concentrations. A history of substance abuse was identified in 14 (82%) subjects and a present tramadol abuse in 8 (47%). These results suggest that fatal intoxications with tramadol may occur unintentionally and that subjects with a history of substance abuse may be at certain risk. Precaution is therefore warranted when prescribing tramadol in such patients.