RT Journal Article SR Electronic T1 Anxiolytic and sedative polypharmacy among US opioid users: a cross-sectional study JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP 370 OP 371 DO 10.1136/rapm-2021-103278 VO 47 IS 6 A1 Brian D Sites A1 Matthew Davis A1 Michael Herrick YR 2022 UL http://rapm.bmj.com/content/47/6/370.abstract AB