Protein hydrolysate formulas are designed for infants who are allergic to cow's milk or soy proteins. Some protein hydrolysate formulas are also elemental with the carbohydrate in easily absorbable forms, such as glucose polymers or monosaccharides, and the fat as both medium-chain and long-chain triglycerides. These are sometimes used in the management of infants with intestinal resection or intractable diarrhea. These formulas can be loosely categorized according to the extent that the protein is hydrolyzed: (1) 100% free amino acid-containing formula (SHS Neocate); (2) extensively hydrolyzed protein-containing formula (Enfamil Nutramigen, Enfamil Pregestimil, Similac Alimentum); and (3) partially hydrolyzed protein-containing formula (Carnation Good Start) (Table 19.1).

All of these protein hydrolysate formulas provide 67–68 kcal/dL energy. These formulas are not routinely recommended for VLBW infants but are used frequently in VLBW infants after intestinal resection resulting from NEC. A recent review by Szajewska concluded there was little evidence to support the use of extensive and partial protein hydrolysate formulas for preterm infants.