  Surveillance of drug overdose deaths relies on death certificates for
identification of the substances that caused death. Drugs and drug classes can
be identified through the International Classification of Diseases, 10th
Revision (ICD-10) codes present on death certificates. However, ICD-10 codes do
not always provide high levels of specificity in drug identification. To
achieve more fine-grained identification of substances on a death certificate,
the free-text cause of death section, completed by the medical certifier, must
be analyzed. Current methods for analyzing free-text death certificates rely
solely on look-up tables for identifying specific substances, which must be
frequently updated and maintained. To improve identification of drugs on death
certificates, a deep learning named-entity recognition model was developed,
which achieved an F1-score of 99.13%. This model can identify new drug
misspellings and novel substances that are not present on current surveillance
look-up tables, enhancing the surveillance of drug overdose deaths.
