Negative feedback control of neonatal serum creatine and increased urinary creatinine excretion after enzyme-inducing drugs.

Abstract

Summary: Creatinine, creatine, and glucaric acid were determined in 24-hr urine samples collected from three groups of newborns on the first, fourth, and seventh day of life. Simultaneously creatine, creatinine, and bilirubin were estimated in serum of cord blood and of venous blood on the fourth and seventh day. Urinary creatinine excretion increased from the low values on the first day to the fourth day levels. In the control infants there was no further increase on the seventh day, on average. In both groups treated with oral nikethamide in addition to simultaneous intramuscularly applied phenobarbital in one group, and to oral sodium phenobarbital solution in the other one, further increase from the fourth to the seventh day was observed so that on the seventh day the creatinine excretion was significantly higher in both treated groups when compared with the seventh day values on the control group. Serum creatine levels were highest on the fourth day; on the seventh day they dropped, but were higher in both treated groups. Urinary creatine excretion showed almost he same tendency as serum creatine levels. Creatioine clearance was not higher in the treated groups. The increases in glucaricacid and creatinine excertion in the treated group were in good orrelation. The pronounced serum billirubin decrease also confirmed the inductive effect of these drugs.Speculation: Serum creatine levels and creatinine excertion is anmsuitable reference in neonates. Enzyme-inducing drugs may increase creatinine excretion, probably by increasing creatine input into the circulation.