Integration of historical clinical data. An example of code-matching between the historical inpatient pharmacy module (PM) and the current inpatient PM, with links to RxNorm. Warfarin, 5 mg oral tablet in the historical inpatient PM had a dispense code of WARF5TU, which matched to a single item in the current inpatient PM. This item had the main Multum drug code (MMDC) 3616, which mapped to RxNorm code 855332, which could now be assigned to the historical code. Once the codes were matched across systems and mapped to RxNorm, a single query across historical and current data could be performed using RxNorm.