ObjectivesCurrently, there are three monotherapy drugs approved by the United States Food and Drug Administration (FDA) for use in intrathecal drug delivery systems (IDDS): morphine, ziconotide, and baclofen. In practice, use includes alternate drugs, drug combinations, and drug concentrations. There is a paucity of real-world data examining prescription patterns for IDDS. Our analysis explores a one-year sample of prescription intrathecal (IT) medications from a large pharmaceutical data base to characterize medication usage in IDDS. Materials and MethodsData were provided by an accredited pharmacy as a deidentified data base of IT drug prescriptions. Statistical analyses included rates of monotherapy vs combination therapies, frequencies of various IT prescriptions, use of on- vs off-label medications, and opioid vs nonopioid formulations. ResultsData were extracted from February 1, 2021 to February 14, 2022. No patients were excluded. The initial sample comprised 49,917 individual IT prescriptions for 32,784 patients. Monotherapies constituted 55.0% of all prescriptions (27,475/49,917). Of these, 23,257 prescriptions (84.6%) were opioid based, with the most common medications being morphine (46.5%), hydromorphone (39.4%), and fentanyl (13.5%). Although 29.3% of all prescriptions were for one of the FDA-approved medications, only 7.9% used FDA-approved concentrations; 9865 patients underwent ≥one prescription change in the study period—16.7% of whom were initially prescribed medications that met the approved, on-label indications for the pump before being switched to off-label concentrations or combinations to address clinical needs. ConclusionsDespite the prevalence of IDDS for managing chronic, intractable pain, minimal data exist on real-world prescription practices. Our study found that FDA-approved IT formulations accounted for the minority of prescriptions, indicating significant practice variation, with off-label prescriptions being common.