On-site medical care in methadone maintenance: associations with health care use and expenditures.

To evaluate whether long-term drug treatment with on-site medical care is associated with diminished inpatient and outpatient service use and expenditures, we linked prospective interview data to concurrent Medicaid claims of drug users in a methadone program with comprehensive medical services. Patient care was classified as follows: long-term (>/=6 months) drug treatment with on-site usual source of medical care (linked care), long-term drug treatment only, or neither. Multivariate analyses adjusted for visit clustering within patients (n = 423, with 1,161 person-years of observation). After adjustment, linked care participants had more outpatient visits (p < .001), fewer emergency department (ED) visits (24% vs. 33%, p = .02) and fewer hospitalizations (27% vs. 40%, p = .002) than the "neither" group. Ambulatory care expenditures in the linked group were increased, whereas expenditures for other services were similar or reduced. Long-term drug treatment with on-site medical care was associated with increased ambulatory care, less ED and inpatient care, and no net increase in expenditures.