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PHENOBARBITAL METABOLISM IN ADULTS AND IN NEWBORN INFANTS
Author(s) -
BORÉUS L. O.,
JALLING B.,
KÅLLBERG N.
Publication year - 1978
Publication title -
acta pædiatrica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 115
eISSN - 1651-2227
pISSN - 0803-5253
DOI - 10.1111/j.1651-2227.1978.tb16302.x
Subject(s) - phenobarbital , metabolite , medicine , urine , excretion , pharmacokinetics , metabolism , drug , drug metabolism , endocrinology , pharmacology , physiology
. Two adult volunteers and four newborn infants were given a single dose of phenobarbital. The output in the urine of unchanged phenobarbital and of the two main metabolites p ‐hydroxy phenobarbital and conjugated p ‐hydroxy phenobarbital was followed during 8 days in the newborns and during 2 or 4 weeks in the adults. The plasma levels were also determined and some pharmacokinetic constants calculated. It was found that the newborn patients excreted unchanged phenobarbital and p ‐hydroxy phenobarbital in the same proportions relative to dose as did the adult volunteers, i.e. 16–17 % unchanged drug and 9–10 % of the metabolite during the first 8 days after administration. On the other hand, there was a clear‐cut age difference in output of conjugated metabolite where the newborns excreted only 5% of the given dose during the 8‐day observation period. The corresponding value for the adults was 15%. It is concluded that a poor conjugating capacity in the newborn may not have any serious consequences with a drug like phenobarbital where major alternative routes of excretion exist (unchanged drug and unconjugated metabolite). The clinical significance of immature drug metabolism in the newborn cannot be determined unless the excretion of all major metabolites and of unchanged drug is taken into consideration.