Abstracts

In the elderly and patients with hypoalbuminemia or renal dysfunction, total phenytoin levels do not accurately reflect serum free phenytoin levels due to altered protein binding. These patients often require direct monitoring of serum free phenytoin. Studies suggest that monitoring phenytoin levels in saliva may provide a feasible alternative to obtaining free phenytoin levels in the blood. Benefits of monitoring saliva phenytoin levels may include decreased cost to the institution, ease of testing, decreased patient discomfort.The purpose of this study is to determine whether saliva concentrations of phenytoin are equivalent to unbound phenytoin levels in the blood in the Veteran population. This study will compare phenytoin levels in paired blood and saliva samples from approximately 30 patients. After meeting eligibility criteria, patients consenting to participate in this study will be required to yield one blood sample and one saliva sample. Saliva samples will be collected immediately following the acquisition of blood samples under the supervision of at least one investigator. Saliva samples will be frozen and stored until all samples are available for analysis. All saliva samples will be quantified using the Beckman Immunoassay Chemistry Analyzer. Secondary endpoints that will be collected include age, serum creatinine, albumin, current medications, concomitant illnesses, time of sample collection and current phenytoin dose. Secondary end points and their impact on the relationship between total serum phenytoin levels and free serum and saliva phenytoin levels will also be reported. Total phenytoin levels as well as secondary end points will be plugged into commonly used pharmacokinetic phenytoin equations to ascertain whether serum free or saliva phenytoin levels correspond more closely with extrapolated serum free phenytoin levels. Currently 5 patients have been enrolled in this study. Preliminary results indicate that saliva phenytoin levels correlate with serum free phenytoin levels Prelimnary results suggest that monitoring phenytoin levels in saliva may provide a feasible alternative to obtaining free phenytoin levels in the blood in the Veteran population.