Quantification of Free Phenytoin by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS).
Phenytoin (diphenylhydantoin) is an anticonvulsant drug that has been used for decades for the treatment of many types of seizures. The drug is highly protein bound and measurement of free-active form of the drug is warranted particularly in patients with conditions that can affect drug protein binding. Here, we describe a LC/MS/MS method for the measurement of free phenytoin. Free drug is separated by ultrafiltration of serum or plasma. Ultrafiltrate is treated with acetonitrile containing internal standard phenytoin d-10 to precipitate proteins. The mixture is centrifuged and supernatant is injected onto LC-MS-MS, and analyzed using multiple reaction monitoring. This method is linear from 0.1 to 4.0 μg/mL and does not demonstrate any significant ion suppression or enhancement.
Methods in molecular biology (Clifton, N.J.)
Anticonvulsants; Chromatography, Liquid; Drug Monitoring; Humans; Phenytoin; Tandem Mass Spectrometry; Ultrafiltration
Anticonvulsants; Drug monitoring
Peat, J., Frazee, C. C., Garg, U. Quantification of Free Phenytoin by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS). Methods in molecular biology (Clifton, N.J.) 1383, 241-246 (2016).