Effect of ultrafiltrate volume on determination of free phenytoin concentration
Related Experiment Video
Updated: Aug 15, 2026

Network Pharmacology Prediction and Metabolomics Validation of the Mechanism of Fructus Phyllanthi against Hyperlipidemia
Published on: April 7, 2023
Gwen A McMillin1, Joetta Juenke, Amitava Dasgupta
1ARUP Institute for Clinical and Experimental Pathology, University of Utah School of Medicine, Salt Lake City, Utah, USA.
Abstract:
Monitoring free phenytoin concentration is clinically useful for patients with uremia, hepatic disease, hypoalbuminemia, and related conditions. Free phenytoin is commonly measured by immunoassay in the protein-free ultrafiltrate prepared by centrifuging serum for 20-30 minutes, using an appropriate ultrafiltration device. We studied the effect of centrifugation time (15-40 minutes) and protein concentrations on ultrafiltration volume, and the related effects on measured free phenytoin concentrations. Temperature was ambient for all studies. The ultrafiltration volumes were directly proportional to centrifugation time and were inversely proportional to the protein concentrations. Although ultrafiltration volume significantly increased with longer centrifugation time, the measured free phenytoin concentrations did not increase proportionately. The concentration of phenytoin in the residual serum retained in the ultrafiltration device did not change proportionally either. Therefore, equilibrium of phenytoin concentrations between the ultrafiltrate and retentate was maintained, regardless of centrifugation time or protein concentration.
More Related Videos
14:39Semi-Targeted Ultra-High-Performance Chromatography Coupled to Mass Spectrometry Analysis of Phenolic Metabolites in Plasma of Elderly Adults
Published on: April 22, 2022
10:30A Generalized Method for Determining Free Soluble Phenolic Acid Composition and Antioxidant Capacity of Cereals and Legumes
Published on: June 10, 2022
Related Concept Videos
Pharmacokinetics in Pediatric Patients: Drug Distribution
Drug Dosing in Renal Diseases: Dose Adjustments Based on Drug Clearance and Elimination Rate Constant
Determination of Michaelis Constant and Maximum Elimination Rate
These parameters can be estimated by analyzing plasma concentration data post-drug administration. A notable example of this application is phenytoin, a drug with capacity-limited kinetics. It's recommended that phenytoin should be administered at two...
Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations
Effect of Hepatic Disease on Pharmacokinetics: Active Drug, Metabolite and Fraction of Metabolized Drug
Factors Affecting Renal Clearance: Drug's Physicochemical Properties and Plasma Levels
One important factor is the drug's molecular size. The kidneys readily excrete smaller molecules below 300 Daltons (Da). On the other hand, molecules weighing between 300 and 500 Da are excreted through both urine and bile. Larger molecules above 500 Da tend to be excreted less...