Indicator Explainer
Phenytoin
A hydantoin derivative and a non-sedative antiepileptic agent with anticonvulsant activity. Phenytoin potentially acts by promoting sodium efflux from neurons located in the motor cortex reducing post-tetanic potentiation at synapses. The reduction of potentiation prevents cortical seizure foci spreading to adjacent areas, stabilizing the threshold against hyperexcitability. In addition, this agent appears to reduce sensitivity of muscle spindles to stretch causing muscle relaxation.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C741. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-20. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also Known As
References
- NCI Thesaurus 26.09d — Phenytoin (C741)
- Source: National Cancer Institute, NCI Thesaurus 26.09d, C741. NCI definition, reproduced without modification under CC BY 4.0.
- Chronic phenytoin toxicity presenting with asterixis, cerebellar signs, and encephalopathy. — Epileptic Disord, 2026-10-13 (PMID 42867881; literature)
- Protective Effects of Phenytoin and Spironolactone against 5-Fluorouracil-induced Alopecia: Involvement of Antioxidant, Anti-inflammatory, and Collagen-regenerative Mechanisms. — Antiinflamm Antiallergy Agents Med Chem, 2026-10-06 (PMID 42864925; literature)
- Electrospun ZIF-8-enhanced fibers for fabric phase extraction of phenytoin from plasma samples followed by high performance liquid chromatography-tandem mass spectrometry analysis. — J Chromatogr B Analyt Technol Biomed Life Sci, 2026-09-30 (PMID 42868770; literature)
- Protective effect of dapagliflozin against phenytoin-induced cerebellar dysfunction and histological alterations in rats: the role of SIRT1/Nrf2/HO-1 pathway. — Naunyn Schmiedebergs Arch Pharmacol, 2026-09-28 (PMID 42803965; literature)