Glycerol phenylbutyrate (Ravicti®) is recommended as an option for use within NHS Wales for use as an adjunctive therapy for chronic management of patients with urea cycle disorders including deficiencies of:

• carbamoyl phosphate synthetase I (CPS);
• ornithine carbamoyltransferase (OTC);
• argininosuccinate synthetase (ASS);
• argininosuccinate lyase (ASL);
• arginase I (ARG)
• and ornithine translocase deficiency hyperornithinaemia-hyperammonaemia homocitrullinuria syndrome (HHH)

who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. Ravicti® must be used with dietary protein restriction and, in some cases, dietary supplements (for example, essential amino acids, arginine, citrulline, protein-free calorie supplements). This recommendation applies only in circumstances where the approved Wales Patient Access Scheme (WPAS) is utilised or where the list/contract price is equivalent or lower than the PAS/WPAS price.