Drug incompatibilities can lead to loss of effectiveness of drugs or to increased risk for undesirable effects that can even be life-threatening. Especially children are at high risk. Databases are an important source of information in routine care to avoid incompatibilities. However, they were supposedly developed considering drugs for use in adults. Thus, we analysed to what extent databases are appropriate for the identification of incompatibilities in intravenous (i.v.) drug therapy in paediatric intensive care. We analysed the information provided by two databases (Database A and B) on all pairs of two drugs prescribed to be administered via the same i.v. access line in a university paediatric intensive care unit during the study period of 50 days. A total of 50 different i.v. drugs was prescribed in 318 different combinations (drug pairs). We found information on (in)compatibilities in 23.0 % (73/318) in Database A and in 31.1 % (99/318) in Database B. Only in 11.0 % (35/318) of the drug pairs, both databases provided information. Considering those drug pairs, in 17.1 % (6/35) Database B indicated compatibility whereas Database A indicated incompatibility. Compatibility information delivered by databases on drugs used in paediatric intensive care is incomplete, heterogeneous, and partly contradictory. Thus, an increased awareness on the strengths and limitations of different databases is necessary to avoid patient harm.