Tetrahydrobiopterin (BH4) responsiveness in neonates with hyperphenylalaninemia: a semi-mechanistically-based, nonlinear mixed-effect modeling.

Neonatal loading studies with tetrahydrobiopterin (BH4) are used to detect hyperphenylalaninemia due to BH4 deficiency by evaluating decreases in blood phenylalanine (Phe) concentrations post BH4 load. BH4 responsiveness in phenylalanine hydroxylase (PAH)-deficient patients introduced a new diagnostic aspect for this test. In older children, a broad spectrum of different levels of responsiveness has been described.

Exposure-clinical response analysis of paricalcitol in patients with chronic kidney disease (stage 5) on hemodialysis or peritoneal dialysis.

Paricalcitol injection and capsules are approved for the prevention and treatment of secondary hyperparathyroidism. Exposure-response analyses were performed to describe paricalcitol pharmacokinetics and the relationship to clinical responses (intact parathyroid hormone [iPTH], serum calcium, and phosphorus) following administration of paricalcitol capsules or injection to patients with chronic kidney disease (stage 5). Paricalcitol pharmacokinetics were similar following intravenous and oral administration with mean oral clearance of 1.