Figure 1.

Rate of posts discussing synthetic opioids on substance message boards and unintentional synthetic opioid overdose deaths, 2010–2016. Note: The rate of unintentional overdose fatalities resulting from synthetic opioids (a category that includes fentanyl and fentanyl analogs but excludes methadone) was ascertained from death certificate data processed through the National Vital Statistics System (underlying cause of death code X40-X44 and a multiple cause of death code of T40.4). Terms used to identify synthetic opioid posts were assembled from the top 40 words identified by the word2vec and fastText algorithms as most semantically similar to “fentanyl” as measured by cosine similarity; lists of the top 20 terms produced by each algorithm were reviewed by an expert and combined to include 34 unique terms: fent, butryfentanyl, fentanils, carfentanil, fentanyls, fentnyl, fetanyl, furanylfentanyl, fentantyl, fentynal, butyryl, lofentanyl, carfentanyl, sufentanil, truckfentanyl, butyrfentanyl, fentanyli, fentynyl, carfent, ocfentanyl, fentayl, furanyl, fentany, fentanyl, acrylfentanyl, carafentanyl, fentynl, sufentanyl, butyr, fentanylso, acetylfentanyl, busfentanyl, fentanayl, fentanil.