Benzodiazepine prescribing patterns and deaths from drug overdose among US veterans receiving opioid analgesics: case-cohort study

OBJECTIVE To study the association between benzodiazepine prescribing patterns including dose, type, and dosing schedule and the risk of death from drug overdose among US veterans receiving opioid analgesics. DESIGN Case-cohort study. SETTING Veterans Health Administration (VHA), 2004-09. PARTICIPANTS US veterans, primarily male, who received opioid analgesics in 2004-09. All veterans who died from a drug overdose (n=2400) while receiving opioid analgesics and a random sample of veterans (n=420,386) who received VHA medical services and opioid analgesics. MAIN OUTCOME MEASURE Death from drug overdose, defined as any intentional, unintentional, or indeterminate death from poisoning caused by any drug, determined by information on cause of death from the National Death Index. RESULTS During the study period 27% (n=112,069) of veterans who received opioid analgesics also received benzodiazepines. About half of the deaths from drug overdose (n=1185) occurred when veterans were concurrently prescribed benzodiazepines and opioids. Risk of death from drug overdose increased with history of benzodiazepine prescription: adjusted hazard ratios were 2.33 (95% confidence interval 2.05 to 2.64) for former prescriptions versus no prescription and 3.86 (3.49 to 4.26) for current prescriptions versus no prescription. Risk of death from drug overdose increased as daily benzodiazepine dose increased. Compared with clonazepam, temazepam was associated with a decreased risk of death from drug overdose (0.63, 0.48 to 0.82). Benzodiazepine dosing schedule was not associated with risk of death from drug overdose. CONCLUSIONS Among veterans receiving opioid analgesics, receipt of benzodiazepines was associated with an increased risk of death from drug overdose in a dose-response fashion.