Prevalence and nature of potential drug–drug interactions among kidney transplant patients in a German intensive care unit

Background Complex polypharmacotherapy makes kidney transplant patients vulnerable to drug-drug interactions (DDIs). Objective To study prevalence and nature of potential DDIs (pDDIs) in kidney transplant patients. Setting Internal medicine ICU, University Hospital RWTH Aachen. Method In this retrospective observational study, pDDIs were identified in the first week after transplant from 1999 to 2010. Patients aged at least 18 years with prescription of at least two drugs were included. Patients with incomplete data were excluded. Data was originally obtained from medical charts. Two Clinical Decision Support Systems (CDSSs) in German language, mediQ and Meona, were used for pDDI identification and severity rating. Main outcome measure PDDIs in each severity level of the CDSSs/100 patient days. Results A total of 252 patients with 37,577 prescriptions were analysed. We found 99 pDDIs from severity levels major/contraindicated in Meona and 299 pDDIs from severity levels clinically relevant/strong in mediQ per 100 patient days. Most important potential consequences of pDDIs in respective severity levels were changes in immunosuppressant drug and potassium levels, nephrotoxicity and cardiac adverse events. Conclusion This study found a high prevalence of pDDIs in the first week after kidney transplant. Medication should be checked for pDDIs to prevent ADEs. It is strongly advisable to closely monitor patients within the first week after transplant for clinical and laboratory parameters and if necessary, change therapy. Physician education on the basis of study findings, DDI check with Clinical Physician Order Entry System/CDSSs and integration of a clinical pharmacist into the ward team should be targeted.