US chiropractors measured changes in pain and disability for chronic low back pain patients receiving treatment with medication-assisted manipulation (MAM) and compared these to changes in a group only receiving spinal manipulation in a prospective cohort study of 68 chronic low back pain patients. Outcomes were measured using the 1998 Version 2.0 American Association of Orthopaedic Surgeons/Council of Musculoskeletal Specialty Societies/Council of Spine Societies Outcomes Data Collection Instruments. The primary outcome variable was change in pain and disability. All patients received an initial 4- to 6-week trial of spinal manipulation therapy (SMT), after which 42 patients received supplemental intervention with MAM and the remaining 26 patients continued with SMT. Low back pain and disability measures favoured the MAM group over the SMT-only group at 3 months. This difference attenuated at 1 year. The relative odds of experiencing a 10-point improvement in pain and disability favoured the MAM group at 3 months and at 1 year.