Abstract
A patient (T.D.) with hyperphenylalaninemia caused by a defect in tetrahydrobiopterin synthesis (NEJM 299: 673, 1978) was treated with 6-methyltetrahydrobiopterin (6MPH4) and tetrahydrobiopterin (BH4) to compare effectiveness. The initial trial of orally administered 6MPH4 at 12 mg/kg/d resulted in an excellent clinical response. After 8 mo of treatment 6MPH4 was stopped because of elevated liver enzymes (SGOT 324, SGPT 468). The liver function tests returned to normal within 1 mo of stopping 6MPH4. Within 3 days of a second trial of 6MPH4 at 12 mg/kg the liver enzymes were abnormal (SGOT 119, SGPT 348). 6MPH4 was then tappered to 4 mg/kg, but deteriorating clinical function required restarting L-dopa + 5-HT to stabilize the clinical status. Treatment with orally administered BH4 (11 mg/kg) resulted in dramatic clinical response similar to 6MPH4 treatment, but without any evidence of liver toxicity after 1 mo of treatment. BH4 and 6MPH4 (∼12mg/kg) caused a lowering of plasma phenylalanine to 1 to 2mg/dl within 1 wk of treatment from pre-treatment levels of 5-10 mg/dl. Measurement of the reduced pterins in plasma by HPLC showed peak levels of 6MPH4 about 14-fold higher than BH4 after oral doses of 4 mg/kg. CSF neurotransmitter metabolites were measured by HPLC on different treatment schedules. The neurotransmitter metabolites levels were not correlated with neurological data.
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Muenzer, J., Milstein, S., Sidbury, J. et al. TREATMENT OF HYPERPHENYLALANINEMIA SECONDARY TO A DEFICIENCY OF BIOPTERIN WITH REDUCED PTERINS. Pediatr Res 18 (Suppl 4), 297 (1984). https://doi.org/10.1203/00006450-198404001-01225
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DOI: https://doi.org/10.1203/00006450-198404001-01225
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