Objectives Patients hospitalized in intensive care units often require multiple drug infusions. Due to limited intravenous accesses, concomitant administration of drugs in the same infusion line is often necessary. Compatibility studies of Y-site administration are available in the literature, but data of several combinations are lacking. Previous work from d’Huart et al. have performed an observation of the administration of injectable drugs in three adults ICUs and identified a list of Y-site administration without compatibility data. The objective of this study was to test the physical compatibility of the main drugs of this list used in pairs in Y-site infusions in critical care units, in order to provide new compatibility data to the literature, and to secure the administration of intravenous drugs. Methods The physical compatibility in Y-site of nine drugs with other drugs commonly used in intensive care units has been tested. Examinations were performed on 75 mixtures after their preparation, after 1 and 4-h storage. This evaluation included a visual examination with a search for precipitation formation, color change, gas formation, and a subvisual evaluation: absorbance measurements by UV-visible spectrophotometry at 350, 410 and 550 nm, and Light Obscuration Particle Count Test. The pH evaluation was performed at each time of analysis. Results Laboratory tests led to an overall compatibility of 68.0% for all mixtures obtained in this study. Nefopam was found to be quite compatible with other drugs (95.0%). Amiodarone hydrochloride (84.6%), acetylsalicylic acid (80.0%), clonidine hydrochloride (75.0%) and insulin (71.4%) were compatible with other drugs too. Atenolol (42.9%), furosemide (25.0%), heparin sodium (25.0%) showed less compatible results. Pantoprazole sodium (0.0%) was not at all compatible with the other drugs analyzed. Conclusions By the results of these laboratory tests, missing compatibility data are now available, providing additional information to the literature.