The Danish National Hospital Medication Register: A Resource for Pharmacoepidemiology.

Background: The Danish National Hospital Medication Register (DHMR), one of the first nationwide in-hospital medication registries in the world, contains detailed information on medication administration and dispensing. Objective: To provide an overview of the information recorded in the DHMR and to highlight its strengths and limitations as a pharmacoepidemiological research tool. Methods: We reviewed the registry´s geographic and clinical specialty coverage and medications recorded according to the main groups of the Anatomical Therapeutic Chemical classification system. Results: From May 2018 through December 2023, the DHMR recorded data on more than 1.9 million unique patients from all approximately 50 public hospitals and associated hospital outpatient clinics, totaling 105.3 million recordings of hospital medication use. The registry records detailed data on the indication for medication, medication type, pharmaceutical form, dosage, and administration time, collected through electronic medical record systems. Although the data quality has not yet been evaluated in a scientific context, some potential limitations are known. These include regional differences in the data collection and a lack of data from certain clinical specialties. Due to its recent establishment in 2018, the registered number of patients treated may still be limited for some rarely used medications. Conclusion: The DHMR is an important new resource for research in Denmark. Combined with the Danish National Prescription Registry, which covers all community pharmacies, it offers access to accurate data on medication exposure in the Danish population. Users should be aware of potential issues with lack of information before 2018.