Tramadol, naloxone, and seizures
We read with great interest the article by Murray, et al. titled "Seizures in Tramadol Overdoses Reported in the ToxIC Registry: Predisposing Factors and the Role of Naloxone" and would like to congratulate them for their work in identifying patients at increased risk for seizure activity in a cohort of patients reported to the ToxIC registry [1] We would like to provide further data from an alternative database, a Regional Poison Center (RPC) which is part of the National Poison Data System (NPDS) to highlight the variability in reported complication rates by database and the inconsistent association of naloxone administration, response to naloxone, and the development of tramadolrelated seizures. We retrospectively reviewed all RPC cases involving tramadol exposure from January 1, 2014 through December 31, 2015. Of the 742 cases reported during this period, 50 (6.7% were associated with seizures, all of which were self limited. This is in stark contrast to the 52.5% seizure rate reported in the present study and more consistent with previous studies utilizing inpatient admission units [2] and the NPDS [3] Naloxone was administered in 93 (12.5% RPC cases with 9 (9.7% involving seizures after administration. One case involved a seizure 5 hours post naloxone administration and another involved a seizure 1 day after discontinuation of a naloxone infusion. Removal of these cases without temporal feasibility revealed a 7.5% seizure rate which was consistent with the baseline rate of 6.7% Of patients receiving naloxone, 23 (24.7% had a documented beneficial response but it is unclear how many, if any, intubations were prevented by its administration. Our data highlight the variability when utilizing different registries such as the ToxIC database and a RPC in evaluating for rates of complications following substance exposures. Because the ToxIC registry involves reporting of cases evaluated at bedside by Medical Toxicologists, these cases often involve more severe illness, as the authors state, and a likely higher rate of complications than those reported to RPCs. Despite the difference in seizure rates, our data corroborate the authors' conclusions regarding the use of naloxone and the development of seizures. Our results indicate no association between the use of naloxone and the development of seizures. In fact, 84 (90.3% patients in our study were administered naloxone and had no subsequent seizure activity. Patients overdosing on tramadol may have seizures regardless of naloxone administration. Finally, we noted an inconsistent beneficial response to naloxone in our data. Given that these data do not support an increased rate of seizures when naloxone is utilized in the treatment tramadol exposures, we advocate for a toxidrome based approach when deciding whether to administer naloxone in suspected tramadol poisoning with a goal to restore respiratory function.
Clinical toxicology