Purpose Two to seven percent of the German adult population has a renal impairment (RI) with an estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73m 2. This often remains unrecognized and adjustment of drug therapy is lacking. To determine renal function in clinical routine, the CKD-EPI equation is used to calculate an indexed eGFR (ml/min/1.73m 2). For drug dosing, it has to be individualized to a non-indexed eGFR (ml/min) by the patient's body surface area. Here, we investigated the number of patients admitted to urological wards of a teaching hospital with RI between July and December 2016. Additionally, we correctly used the eGFR non-indexed for drug and dosage adjustments and to analyse the use of renal risk drugs (RRD) and renal drug-related problems (rDRP). Methods In a retrospective observational study, urological patients with pharmacist-led medication reconciliation at hospital admission and eGFR indexed (CKD-EPI) of 15-59 ml/min/1.73m 2 were identified. Indexed eGFR (ml/min/1.73m 2) was recalculated with body surface area to non-indexed eGFR (ml/min) for correct drug dosing. Medication at admission was reviewed for RRD and based on the eGFR non-indexed for rDRP, e.g. inappropriate dose or contraindication. Results Of 1320 screened patients, 270 (20.5%) presented with an eGFR indexed of 15-59 ml/min/1.73m 2. After readjustment, 203 (15.4%) patients had an eGFR non-indexed of 15-59 ml/min. Of these, 190 (93.6%) used ≥ 1 drugs at admission with 660 of 1209 (54.7%) drugs classified as RRD. At least one rDRP was identified in 115 (60.5%) patients concerning 264 (21.8%) drugs. Conclusion Renal impairment is a common risk factor for medication safety in urologic patients admitted to a hospital. Considerable shifts were seen in eGFR-categories when correctly calculating eGFR non-indexed for drug dosing purposes. The fact that more than half of the study patients showed rDRP at hospital admission underlines the need to consider this risk factor appropriately.

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