Aim: Although there is a high risk of gastrointestinal (GI) bleeding in the elderly, few studies have quantified the impact of risk factors on GI complications in elderly nonsteroidal anti-inflammatory drug (NSAID) users. This study aimed to develop and validate a risk prediction score to identify high-risk elderly patients using NSAID for severe GI complications. Methods: We used the following two Korean claims datasets: customized data with an enrollment period 2016–2017 for model development, and the sample data in 2019 for external validation. We conducted a nested case-control study for model development and validation. NSAID users were identified as the elderly (≥ 65 years) who received NSAIDs for more than 30 days. Patients who experienced serious GI complications, defined as hospitalizations or emergency department visits, were diagnosed with GI bleeding or perforation. We derived a model using logistic regression and cross-validation. Results: In the external validation cohort, we identified 372 cases from 254,551 patients. We identified 8,176 cases and 81,760 controls with a 1:10 matched follow-up period in the derivation cohort. In the external validation cohort, we identified 372 cases from 254,551 patients. The risk predictors were high-dose NSAIDs, NSAID type, complicated GI ulcer history, male sex, concomitant gastroprotective agents, relevant co-medications, severe renal disease, and cirrhosis. Area under the receiver operating characteristic curves was 0.77 (95% confidence interval, 0.75–0.80) in the external validation dataset. Conclusion: The prediction model may be a useful tool for reducing the risk of serious GI complications by identifying high-risk elderly patients.

Aim: To analyze the effects of CYP3A5 polymorphism on liver function after LT and to characterize the pharmacokinetics of tacrolimus after conversion from a twice-daily regimen to a once-daily extended-release formulation. Methods: A prospective open-label study included 60 stable liver transplant recipients who underwent 1:1 conversion from twice-daily tacrolimus to once-daily tacrolimus. All participants were genotyped for CYP3A5 polymorphism. The study was registered at ClinicalTrials.gov (NCT 02882113). Results: Twenty-eight patients were enrolled in the CYP3A5 expressor group and 32 in the non-expressor group. Although there was no statistical difference, incidence of liver dysfunction was higher in the expressor group than in the non-expressor group when converted to once-daily extended-release tacrolimus (P=0.088). No biopsy-proven acute rejection, graft failure, and mortality were observed in either group. The decrease in dose-adjusted trough level (- 42.9% vs. - 26.1%) and dose/kg-adjusted trough level of tacrolimus (- 40.0% vs. - 23.7%) was significantly greater in the expressor group than in the non-expressors after the conversion. The absorption of the tacrolimus in the non-expressor group was slower than in the expressors. In line with this observation, the AUC for once-daily tacrolimus correlated with Cmin in the non-expressors and Cmax in the expressors. Conclusions: Determination of CYP3A5 genotype in liver transplant recipients might be helpful in prediction of tacrolimus pharmacokinetics after conversion from a twice-daily regimen to a once-daily formulation.