In subject 3, the 3-day trial of NCG showed an encouraging biochemical response that a longer trial was planned. Following baseline (day 0) measurement of ammonia, urea, and amino acids, she was prescribed NCG 100 mg/kg/d.
When a marked decrease in ammonia and glutamine was again observed, the sodium phenylbutyrate (Buphenyl) daily dose was tapered in 500 mg decrements over the ensuing 6 weeks. In a single instance (day 10), due to parental error, the phenylbutyrate dose was unintentionally reduced by 1500 mg/day, and this error was not identified until the subsequent clinical assessment. She remained clinically well throughout.