Abstract
Phenylketonuria (PKU) is an inherited metabolic disorder that results from reduced phenylalanine hydroxylase (PAH) activity. Historically, PKU treatment has involved a phenylalanine-restricted diet substituting high-protein foods with medical food. Despite the treatment's success, diet adherence remains problematic. Sapropterin dihydrochloride* is a formulation of tetrahydrobiopterin (BH4), a cofactor required for PAH activity. Clinical trials demonstrate that, in a subset of PKU patients, sapropterin dihydrochloride enhances PAH activity, leading to better tolerance of dietary phenylalanine, hence natural protein. The present recommendations, based on experience during clinical trials, are intended to guide nutrition specialists overseeing the dietary adjustments associated with sapropterin dihydrochloride therapy.