Denmark has a long tradition of creating nationwide administrative and health registries. ^{1, 2} Examples include its registries on causes of death, ³ hospitalizations ⁴ and cancer, ⁵ and on socioeconomic parameters such as income ⁶ and education. ⁷ A registry central to Danish pharmacoepidemiology is the Register of Medicinal Product Statistics, established in 1994. This registry includes data on all drugs sold in primary care or purchased for use in Danish hospitals. Whereas aggregate data on gross sales of drugs are freely available online [www.medstat.dk], ⁸ individual-level data on prescriptions filled by Danish residents at community pharmacies are available as an independent sub-registry—the National Prescription Registry (NPR). ⁹ NPR data have been available to researchers through Statistics Denmark since 2003, and more recently also through the Danish Health Data Authority. Given these recent changes in data access and the need to evaluate the Registry’s strengths and limitations, this data resource profile provides a review of the NPR, with emphasis on its role in research.

Objective To assess rates of cardiovascular and haemostatic events in the first 28 days after vaccination with the Oxford-AstraZeneca vaccine ChAdOx1-S in Denmark and Norway and to compare them with rates observed in the general populations. Design Population based cohort study. Setting Nationwide healthcare registers in Denmark and Norway. Participants All people aged 18-65 years who received a first vaccination with ChAdOx1-S from 9 February 2021 to 11 March 2021. The general populations of Denmark (2016-18) and Norway (2018-19) served as comparator cohorts. Main outcome measures Observed 28 day rates of hospital contacts for incident arterial events, venous thromboembolism, thrombocytopenia/coagulation disorders, and bleeding among vaccinated people compared with expected rates, based on national age and sex specific background rates from the general populations of the two countries. Results The vaccinated cohorts comprised 148 792 people in Denmark (median age 45 years, 80% women) and 132 472 in Norway (median age 44 years, 78% women), who received their first dose of ChAdOx1-S. Among 281 264 people who received ChAdOx1-S, the standardised morbidity ratio for arterial events was 0.97 (95% confidence interval 0.77 to 1.20). 59 venous thromboembolic events were observed in the vaccinated cohort compared with 30 expected based on the incidence rates in the general population, corresponding to a standardised morbidity ratio of 1.97 (1.50 to 2.54) and 11 (5.6 to 17.0) excess events per 100 000 vaccinations. A higher than expected rate of cerebral venous thrombosis was observed: standardised morbidity ratio 20.25 (8.14 to 41.73); an excess of 2.5 (0.9 to 5.2) events per 100 000 vaccinations. The standardised morbidity ratio for any thrombocytopenia/coagulation disorders was 1.52 (0.97 to 2.25) and for any bleeding was 1.23 (0.97 to 1.55). 15 deaths were observed in the vaccine cohort compared with 44 expected. Conclusions Among recipients of ChAdOx1-S, increased rates of venous thromboembolic events, including cerebral venous thrombosis, were observed. For the remaining safety outcomes, results were largely reassuring, with slightly higher rates of thrombocytopenia/coagulation disorders and bleeding, which could be influenced by increased surveillance of vaccine recipients. The absolute risks of venous thromboembolic events were, however, small, and the findings should be interpreted in the light of the proven beneficial effects of the vaccine, the context of the given country, and the limitations to the generalisability of the study findings.

Importance Hospital readmissions are common among patients receiving multiple medications, with considerable costs to the patients and society. Objective To determine whether a multifaceted pharmacist intervention based on medication review, patient interview, and follow-up can reduce the number of readmissions and emergency department (ED) visits. Design, Setting, and Participants This randomized clinical multicenter study (Odense Pharmacist Trial Investigating Medication Interventions at Sector Transfer [OPTIMIST]) enrolled patients from September 1, 2013, through April 23, 2015, with a follow-up of 6 months completed on October 31, 2015. Consecutive medical patients in an acute admission ward who were 18 years or older and who used 5 or more medications were invited to participate. Of 1873 patients invited to participate, 1499 (80.0%) accepted. The medication review and patient interview were conducted in the hospital and followed up in collaboration with primary care. Analysis was based on intention to treat. Interventions The patients were randomized into 3 groups receiving usual care (no intervention), a basic intervention (medication review), and an extended intervention (medication review, 3 motivational interviews, and follow-up with the primary care physician, pharmacy, and nursing home). Main Outcomes and Measures The prespecified primary outcomes were readmission within 30 or 180 days and ED visits within 180 days. The primary composite end point was readmission or an ED visit within 180 days. Secondary outcomes were drug-related readmissions within 30 and 180 days after inclusion, and all-cause mortality and drug-related mortality. Results A total of 1467 patients (679 men [46.3%] and 788 women [53.7%]; median age, 72 years; interquartile range, 63-80 years) were part of the primary analysis, including 498 randomized to usual care, 493 randomized to the basic intervention, and 476 randomized to the extended intervention. The extended intervention had a significant effect on the numbers of patients who were readmitted within 30 days (hazard ratio [HR], 0.62; 95% CI, 0.46-0.84) or within 180 days (HR, 0.75; 95% CI, 0.62-0.90) after inclusion and on the number of patients who experienced the primary composite end point (HR, 0.77; 95% CI, 0.64-0.93). The study showed a nonsignificant reduction in drug-related readmissions within 30 days (HR, 0.65; 95% CI, 0.39-1.09) and within 180 days (HR, 0.80; 95% CI, 0.59-1.08) after inclusion and in deaths (HR, 0.83; 95% CI, 0.22-3.11). The number needed to treat to achieve the primary composite outcome for the extended intervention (vs usual care) was 12. Conclusions and Relevance A multifaceted clinical pharmacist intervention may reduce the number of ED visits and hospital readmissions. Trial Registration clinicaltrials.gov Identifier:NCT03079375

Hydrochlorothiazide, one of the most frequently used diuretic and antihypertensive drugs in the United States and Western Europe, is photosensitizing and has previously been linked to lip cancer. To examine the association between hydrochlorothiazide use and the risk of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). From the Danish Cancer Registry, we identified patients (cases) with nonmelanoma skin cancer (NMSC) during 2004-2012. Controls were matched 1:20 by age and sex. Cumulative hydrochlorothiazide use (in 1995-2012) was assessed from the Danish Prescription Registry. Using conditional logistic regression, we calculated odds ratios (ORs) for BCC and SCC associated with hydrochlorothiazide use. High use of hydrochlorothiazide (≥50,000 mg) was associated with ORs of 1.29 (95% confidence interval [CI], 1.23-1.35) for BCC and 3.98 (95% CI, 3.68-4.31) for SCC. We found clear dose-response relationships between hydrochlorothiazide use and both BCC and SCC; the highest cumulative dose category (≥200,000 mg of HCTZ) had ORs of 1.54 (95% CI, 1.38-1.71) and 7.38 (95% CI, 6.32-8.60) for BCC and SCC, respectively. Use of other diuretics and antihypertensives was not associated with NMSC. No data on sun exposure were available. Hydrochlorothiazide use is associated with a substantially increased risk of NMSC, especially SCC.