Appropriate medication of intensive care patients is complicated by disturbed organ functions and organ failure, pathophysiological changes in severely ill patients as well as possible sepsis, ongoing haemodialysis for renal and hepatic insufficiency, varying pharmacokinetics/-dynamics (PK/PD) of drugs as well as numerous drug interactions.Illustration of an interdisciplinary approach in daily clinical practice to optimise regular "polymedication" as well as the ongoing medication of patients prior to surgical interventions as indicated and as part of the appropriate peri- and postoperative intensive care management.A so-called "drug interaction stewardship" (DIS) is very similar to the already established "antibiotic stewardship" (ABS) during daily clinical routine of an intensive care unit and has been implemented. In addition, therapeutic drug monitoring (TDM) has been extended to antibiotics/antimycotics (such as meropenem, piperacillin-tazobactam, ceftazidime, linezolide, voriconazole, fluconazole, caspofungin), for which TDM had not yet been established. This was in a consecutive cohort of patients with abdominal surgery over a defined time period and was part of a systematic clinical single centre observational study (tertiary centre).From 01 - 2012 to 08 - 2016, 1,454 single drug patient consultations led to 385 (26.5%) changes in medical treatment, which had been previously initiated by an experienced intensive care physician. Most frequently in 156 cases (10.7%) this was due to newly calculated PK/PD. Analysis of 2,333 TDM samples resulted in a minimum serum level within the adequate range in 1,130 cases (48.4%). In 427 cases (18.3%), the drug serum level was too low and in 776 subjects (33.3%), prompting a change in the type, dose, dose interval and application route.DIS and TDM provide a high rate of detection of unwanted drug interactions and inappropriate drug levels in surgical intensive care patients and help to assure targeted therapy changes.