title: Estimation of plasma unbound phenobarbital concentration by using mixed saliva.
abstract: Relationships among plasma total (Ct), plasma protein unbound (Cf) and mixed salivary (Cs) concentrations of phenobarbital (PB) were studied in 29 epileptic patients. A highly significant correlation was observed between Ct and Cf. Although a significant correlation was observed between Cf and Cs, Cs/Cf ratio was only 0.63. When Cs was corrected by using pKa (7.41) and pH of saliva to estimate free PB concentration (Cest f), a highly significant correlation was obtained between Cf and Cest f, and Cest f/Cr ratio was 0.96. The temporal course of Cest f obtained from Cs after an oral single dose of 50 mg PB in a healthy adult male volunteer was approximated as a triexponential equation. The peak time was 2 hr after ingestion and apparent half life was 66 hr. The prediction of minimum concentrations at steady state on the basis of these parameters corresponded well with actually obtained Cest f following repetitive administration of PB.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001798:Blood Proteins / Q000378:metabolism; D002648:Child; D004827:Epilepsy / Q000378:metabolism*; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008433:Mathematics; D008722:Methods; D008875:Middle Aged; D010634:Phenobarbital / Q000097:blood / Q000378:metabolism*; D012463:Saliva / Q000378:metabolism*; D013997:Time Factors
chemical_list: D001798:Blood Proteins; D010634:Phenobarbital