Indications: Phenylketonuria. Tetrahydrobiopterin deficiency

Cautions: monitor blood-phenylalanine concentration before and after first week of treatment—if unsatisfactory response increase dose at weekly intervals to max. dose and monitor blood-phenylalanine concentration weekly; discontinue treatment if unsatisfactory response after 1 month; monitor blood-phenylalanine and tyrosine concentrations 1–2 weeks after dose adjustment and during treatment; history of convulsions.

Side Effects: diarrhoea, vomiting, abdominal pain, nasal congestion, cough, pharyngolaryngeal pain, headache; also reported hypersensitivity reactions.

Dose: Phenylketonuria (specialist use only), by mouth, ADULT and CHILD over 4 years, initially 10 mg/kg once daily, preferably in the morning, adjusted according to response; usual dose 5–20 mg/kg daily.

Tetrahydrobiopterin deficiency (specialist use only), by mouth, ADULT and CHILD initially 2–5 mg/kg once daily, preferably in the morning, adjusted according to response; max. 20 mg/kg daily; total daily dose may alternatively be given in 2–3 divided doses.