Medications That Increase Osmolality and Compromise the Safety of Enteral Feeding in Preterm Infants

Background: Medications added to preterm milk feeds have the potential to raise osmolality, causing feed intolerance and necrotizing enterocolitis.

Objective: The aim of this study was to evaluate changes in the osmolality of milk feeds and water with 14 medications and the diluent amounts required to keep the osmolality below the safety threshold of ≤450 mOsm/kg. Changes in the osmolality of milk with medications while on continuous infusion over 2 and 4 h were determined.

Methods: This study was designed to measure the osmolality of 14 commonly used medications in preterm infants both neat and when supplemented with expressed breast milk (EBM), EBM with fortifier (EBMF), preterm formula (PTF), and water. Dose-effect curves were plotted, and the volume of each diluent was calculated to keep the osmolality ≤450 mOsm/kg. Time-effect curves were plotted at 2 and 4 h for each medication for both EBM and EBMF.

Results: Neat osmolality of all except 5 medications were above 2,000 mOsm/kg. The osmolality rose with decreasing proportions of diluents used, depicting an indirect curvilinear relationship between the increasing dilution and osmolality for all except 2 medications. As a diluent, EBM was required in lower dilutions than EBMF. Dilutions needed for additives with PTF were very similar to those of EBM. The change in osmolality over time with additives was statistically significant for EBMF.

Conclusions: EBM and PTF were found to be safer diluents than EBMF for enteral additives. The practice of keeping milk feeds with medications for continuous feeding is safe for a period of 4 h in EBM.