title: Quantification of Free Phenytoin by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS).
abstract: 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.
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Mercy Hospitals and Clinics, 2401 Gillham Road, Kansas City, MO, 64108, USA.
authors.forename: Judy
authors.initials: J
authors.lastname: Peat
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Mercy Hospitals and Clinics, 2401 Gillham Road, Kansas City, MO, 64108, USA.
authors.forename: Clint
authors.initials: C
authors.lastname: Frazee
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Mercy Hospitals and Clinics, 2401 Gillham Road, Kansas City, MO, 64108, USA. ugarg@cmh.edu.
authors.forename: Uttam
authors.initials: U
authors.lastname: Garg
mesh_terms: D000927:Anticonvulsants / Q000032:analysis / Q000097:blood*; D002853:Chromatography, Liquid / Q000379:methods; D016903:Drug Monitoring / Q000379:methods; D006801:Humans; D010672:Phenytoin / Q000032:analysis / Q000097:blood*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014462:Ultrafiltration / Q000379:methods
chemical_list: D000927:Anticonvulsants; D010672:Phenytoin
keywords: Convulsions; Epilepsy; Free phenytoin; Mass spectrometry; Phenytoin; Seizures