Phenytoin metabolism in subjects with long and short plasma half-lives.
Normal adult men with long and short phenytoin plasma half-lives were given 300-mg oral doses of phenytoin once daily for 15 days. Plasma levels of phenytoin (DPH) and its major metabolite (p-HPPH) were measured during the period of drug administration and for 5 days thereafter. Average steady-state plasma levels of DPH rose to 13.4 micrograms/ml in the long half-life group, compared with 3.6 micrograms/ml in the short half-life group. HPPH levels in the long half-life group were about one half of those observed in the short half-life group. The DPH/HPPH ratios in plasma specimens showed excellent correlation with the plasma half-lives of DPH and average steady-state levels, suggesting that this ratio could provide guidance in the selection of optimum dosage regimens for problem patients.
D000328:Adult; D006207:Half-Life; D006801:Humans; D008297:Male; D008875:Middle Aged; D010672:Phenytoin / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism* / Q000652:urine
C027364:5-(3-hydroxyphenyl)-5-phenylhydantoin; D010672:Phenytoin