Eleven percent of patients in the buprenorphine group ( 95 % CI , 6 % -19 % ) used inpatient addiction treatment services , whereas 37 % in the referral group ( 95 % CI , 27 % -48 % ) and 35 % in the brief intervention group ( 95 % CI , 25 % -37 % ) used inpatient addiction treatment services ( P < .001 ) .