Intravenous medications are frequently administered through shared catheter lines in neonatal intensive care units (NICUs) due to the limited venous access in preterm infants, raising concerns about drug incompatibilities that may cause serious complications. Hydrocortisone sodium (HDC), ampicillin (ABPC), and cefotaxime (CTX) are commonly used in NICUs and are often co-administered with unfractionated heparin (UFH), which is routinely infused to prevent catheter occlusion. This study evaluated the physicochemical compatibility of HDC, ABPC, and CTX when mixed with UFH. Each drug was combined with UFH at equal volumes, and the mixtures were assessed immediately and after 3 h of storage by visual inspection, pH measurement, UV absorbance, and HPLC-UV analysis. No precipitation, turbidity, or color changes were observed in any mixture, and UV absorbance showed no relevant deviations compared with controls. Slight pH variations were detected but remained within acceptable limits. In semi-quantitative HPLC analysis, relative peak area changes were all below 10%, indicating no major degradation of the drugs. These findings suggest that HDC, ABPC, and CTX maintain acceptable physicochemical compatibility when co-administered with UFH, supporting their safe concomitant use in NICU practice.

In neonatal intensive care units (NICUs), limited vascular access often necessitates the co-administration of multiple intravenous medications through a single line, increasing the risk of physicochemical incompatibility. Doxapram hydrochloride (DOP), a respiratory stimulant used when caffeine therapy is insufficient, is continuously infused and frequently requires Y-site administration with other drugs. This study systematically evaluated the compatibility of seven commonly used NICU medications—midazolam (MDZ), dalteparin sodium (DLT), cefazolin, cefepime (CFPM), vancomycin, fosfluconazole, and famotidine—under conditions simulating co-administration through the side port of a continuous DOP infusion. Visual inspection, UV absorbance, pH measurement, and HPLC/UV analysis were performed at 0 and 3 h, with extended evaluation to 24 h for only MDZ and DLT. All mixtures showed acceptable physicochemical compatibility within 3 h, and MDZ and DLT remained stable for 24 h, indicating feasibility for co-infusion in the same syringe. In HPLC/UV analysis, the CFPM–DOP mixture exhibited a marked artifactual increase in DOP peak area, likely due to pH-dependent chromatographic behavior changing rather than true incompatibility. These findings provide practical compatibility data for NICU drug administration and offer a methodological framework for evaluating untested drug combinations, contributing to safer and more efficient intravenous therapy in preterm infants.