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Urine and plasma free phenytoin concentration correlation
Author(s) -
Casto Daniel T,
Ludden Thomas M,
Bertoni John M,
Littlefield Louis C,
Sagraves Rosalie A,
Mackey Ray W
Publication year - 1982
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1982.213
Subject(s) - urine , phenytoin , albuminuria , chemistry , chromatography , urine collection device , plasma concentration , positive correlation , negative correlation , dialysis , free flow , endocrinology , medicine , renal function , epilepsy , biochemistry , physics , psychiatry , mechanics
In an attempt to find a simple, noninvasive method for estimating the plasma free concentration (Cp f ) of phenytoin (PHT), the relationship between urine PHT concentration (Cu) and Cp f was studied in 40 epileptic patients who were 6 to 50 yr old. Cu was determined by gas‐liquid chromatography and Cp f by equilibrium dialysis at 37°. Cu was generally greater than Cp f , but correlation between the two was strong (r 2 = 0.876) and in the same range as previously published results for saliva and Cp f . Correlation of Cu with Cp f was not influenced by patient age, urine pH, or urine flow rate. In 24 patients timed urine collections were obtained and calculated renal clearances of PHT were shown to increase in proportion to urine flow rates. Although it is not known if renal impairment and albuminuria will alter the relationship between Cu and Cp f , it appears that Cu may be useful in estimating the concentration of pharmacologically active PHT in plasma. Clinical Pharmacology and Therapeutics (1982) 32, 628–634; doi: 10.1038/clpt.1982.213