Overview

Phenytoin is classified as a hydantoin derivative and despite its narrow therapeutic index, it is one of the most commonly used anticonvulsants. Since it's introduction about 80 years ago, phenytoin has not only been established as an effective anti-epileptic, but has also been investigated for several other indications such as bipolar disorder, retina protection, and wound healing. Clinicians are advised to initiate therapeutic drug monitoring in patients who require phenytoin since even small deviations from the recommended therapeutic range can lead to suboptimal treatment, or adverse effects. Both parenteral and oral formulations of phenytoin are available on the market.

Indication

Phenytoin is indicated to treat grand mal seizures, complex partial seizures, and to prevent and treat seizures during or following neurosurgery. Injectable phenytoin and Fosphenytoin, which is the phosphate ester prodrug formulation of phenytoin, are indicated to treat tonic-clonic status epilepticus, and for the prevention and treatment of seizures occurring during neurosurgery.

Associated Conditions

Complex Partial Seizure Disorder
Generalized Tonic-Clonic Seizures
Grand Mal Status Epilepticus
Jacksonian epilepsy
Partial-Onset Seizures
Petit Mal Epilepsy
Seizure Disorder, Post Traumatic
Seizures
Status; Epilepticus, Tonic-clonic
Temporal Lobe Epilepsy (TLE)
Convulsive disorders

Research Report

Published: Aug 11, 2025

A Comprehensive Monograph on Phenytoin (DB00252)

1.0 Introduction and Executive Summary

1.1 Overview of Phenytoin's Stature

Phenytoin stands as a foundational, first-generation antiepileptic drug (AED) that has been a cornerstone in the management of epilepsy for over eight decades.[1] First synthesized in 1908 and recognized for its anticonvulsant properties in 1938, it represented a paradigm shift in neurologic therapy by offering effective seizure control without the profound sedative effects of its predecessors, like phenobarbital.[2] Its enduring importance is underscored by its inclusion on the World Health Organization's List of Essential Medicines, a testament to its established efficacy, widespread availability, and critical role in global health.[2] Despite the development of numerous newer AEDs with more favorable pharmacokinetic profiles, phenytoin remains a vital therapeutic option, particularly for tonic-clonic and focal seizures, as well as in the acute management of status epilepticus.[1]

1.2 The Central Therapeutic Dichotomy

Continue reading the full research report

Clinical Trials

Title	Posted	Study ID	Phase	Status	Sponsor
Early Post-Traumatic Seizures Prevention Trial (E-PTS Trial)	2025/07/18	NCT07072624	Not Applicable	Recruiting	All India Institute of Medical Sciences, Jodhpur
A Study to Evaluate VH4524184 Tablet Absorption, Effects of Food, and Interactions With Other Drugs in Healthy Adults	2025/07/15	NCT07066722	Not Applicable	Not yet recruiting	ViiV Healthcare
Drug-Drug Interaction Study of Casdatifan in Healthy Adult Participants (ARC-29)	2025/04/09	NCT06919991	Phase 1	Recruiting	Arcus Biosciences, Inc.
Effect of Phenytoin or Itraconazole on How BGB-16673 is Absorbed and Removed From the Body in Healthy Participants	2025/04/02	NCT06906809	Phase 1	Recruiting	BeiGene
A Clinical Study of Belzutifan (MK-6482) Alone or With Phenytoin in Healthy Participants (CA46602/MK-6482-035)	2025/04/01	NCT06903715	Phase 1	Completed	Merck Sharp & Dohme LLC
A Study of the Effect of Itraconazole and Phenytoin on MK-1084 in Healthy Adults (MK-1084-008)	2024/12/06	NCT06719557	Phase 1	Completed	Merck Sharp & Dohme LLC
Effect of Phenytoin Cream on Wound Healing After Anal Fissure Surgery.	2024/10/09	NCT06633185	Phase 1	Completed	Mansoura University
A Study to Evaluate the Effects of Phenytoin and Itraconazole on Sonrotoclax (BGB-11417) in Healthy Volunteers	2024/08/07	NCT06543043	Phase 1	Completed	BeiGene
A Study to Learn How Different Forms of The Study Medicine Called Phenytoin Are Taken up Into the Blood in Healthy Adults	2024/06/20	NCT06466473	Phase 1	Completed	Pfizer
Drug-Drug Interaction (DDI) Study of Leramistat in Healthy Adult Subjects	2024/04/23	NCT06379958	Phase 1	Recruiting	Modern Biosciences Ltd

FDA Drug Approvals

Approved Product	Manufacturer	NDC Code	Route	Strength	Effective Date
Phenytoin	REMEDYREPACK INC.	70518-0841	ORAL	50 mg in 1 1	2/13/2024
Extended Phenytoin Sodium	Aurobindo Pharma Limited	65862-692	ORAL	100 mg in 1 1	9/21/2023
Phenytoin	Taro Pharmaceuticals U.S.A., Inc	51672-4146	ORAL	50 mg in 1 1	6/28/2022
Phenytoin Sodium	Golden State Medical Supply, Inc.	51407-982	ORAL	100 mg in 1 1	5/27/2025
Phenytoin Sodium	REMEDYREPACK INC.	70518-1776	ORAL	100 mg in 1 1	2/22/2024
Dilantin Infatabs	Parke-Davis Div of Pfizer Inc	0071-0007	ORAL	50 mg in 1 1	3/21/2022
Phenytoin Sodium	Hikma Pharmaceuticals USA Inc.	0641-0493	INTRAMUSCULAR, INTRAVENOUS	50 mg in 1 mL	1/18/2024
Extended Phenytoin Sodium	Major Pharmaceuticals	0904-6187	ORAL	100 mg in 1 1	4/1/2024
Extended Phenytoin Sodium	Aphena Pharma Solutions - Tennessee, LLC	71610-479	ORAL	100 mg in 1 1	11/12/2020
Phenytoin	American Health Packaging	60687-275	ORAL	125 mg in 5 mL	10/31/2022

EMA Drug Approvals

Approved Product	Authorization Holder	Status	Issued Date
No EMA approvals found for this drug.

HSA Drug Approvals

Approved Product	Manufacturer	Approval Number	Dosage Form	Strength	Approval Date
DILANTIN CAPSULE 100 mg	Pfizer Pharmaceuticals LLC	SIN09208P	CAPSULE	100 mg	2/25/1997
DBL PHENYTOIN INJECTION BP 50 mg/ml	Siegfried Hameln GmbH	SIN08183P	INJECTION	50 mg/ml	5/22/1995
Dilantin 125® (Phenytoin Oral Suspension, USP) 125mg/5ml	Pharmacia and Upjohn Company LLC	SIN13114P	SUSPENSION	125.00mg/5ml	6/6/2005
DILANTIN CAPSULE 30 mg	Pfizer Pharmaceuticals LLC	SIN06056P	CAPSULE	30 mg	5/22/1991
PHARMANIAGA PHENYTOIN SODIUM SOLUTION FOR INJECTION 250MG/5ML	Pharmaniaga LifeScience Sdn. Bhd.	SIN16560P	INJECTION, SOLUTION	250mg/5mL	8/2/2022

NMPA Drug Approvals

Approved Product	Company	Approval Number	Drug Type	Dosage Form	Approval Date
No NMPA approvals found for this drug.

PPB Drug Approvals

Approved Product	Registration No.	Company	Licence No.	Strength	Registration Date
No PPB approvals found for this drug.

TGA Drug Approvals

Approved Product	ARTG ID	Sponsor	Registration Type	Status	Registration Date
PHENYTOIN JUNO (phenytoin sodium) 250mg/ 5mL injection ampoule	117865	Juno Pharmaceuticals Pty Ltd	Medicine	A	12/22/2006
DBL PHENYTOIN INJECTION 250mg/5mL ampoule	46943	Pfizer Australia Pty Ltd	Medicine	A	11/30/1993
DILANTIN PAEDIATRIC SUSPENSION phenytoin 30mg/5mL oral liquid bottle	14309	Viatris Pty Ltd	Medicine	A	9/20/1991
DILANTIN phenytoin sodium 100 mg capsule bottle	295265	Viatris Pty Ltd	Medicine	A	12/11/2017
DBL PHENYTOIN INJECTION 100mg/2mL ampoule	46942	Pfizer Australia Pty Ltd	Medicine	A	11/30/1993
PHENYTOIN JUNO (phenytoin sodium) 100mg/ 2mL injection ampoule	117872	Juno Pharmaceuticals Pty Ltd	Medicine	A	12/22/2006
DILATIN phenytoin sodium 30 mg capsule bottle	295264	Viatris Pty Ltd	Medicine	A	12/11/2017
DILANTIN INFATABS 50 mg chewable tablet bottle	297268	Viatris Pty Ltd	Medicine	A	7/31/2018

Health Canada Drug Approvals

Approved Product	Company	DIN	Dosage Form	Strength	Market Date
DILANTIN W PHENOBARBITAL 15MG	parke-davis division, warner-lambert canada inc.	00275131	Capsule - Oral	100 MG / CAP	12/31/1951
PHENYTOIN SODIUM INJECTION USP	hikma canada limited	02431378	Solution - Intramuscular , Intravenous	50 MG / ML	3/12/2015
TARO-PHENYTOIN	Taro Pharmaceuticals Inc	02468255	Capsule - Oral	100 MG	N/A
PHENYTOIN SODIUM INJECTION USP	Sandoz Canada, Inc.	00780626	Liquid - Intramuscular , Intravenous	50 MG / ML	12/31/1988
PHENYTOIN SODIUM INJECTION USP	omega laboratories limited	00498335	Solution - Intramuscular , Intravenous	50 MG / ML	12/31/1992
DILANTIN W PHENOBARBITAL 30MG CAP	parke-davis division, warner-lambert canada inc.	00439770	Capsule - Oral	100 MG / CAP	12/31/1969
NOVO-PHENYTOIN CAP 100MG	novopharm limited	00037435	Capsule - Oral	100 MG	12/31/1966
PHENYTOIN SODIUM	aa pharma inc	02460912	Capsule - Oral	100 MG	8/16/2017
DILANTIN-30 SUSPENSION	BGP Pharma ULC	00023442	Suspension - Oral	30 MG / 5 ML	12/31/1968
DILANTIN INJ 50MG/ML	parke-davis division, warner-lambert canada inc.	00245453	Liquid - Intravenous , Intramuscular	250 MG / 5 ML	12/31/1972

CIMA AEMPS Drug Approvals

Approved Product	Company	Registration Number	Pharmaceutical Form	Prescription Type	Status
SINERGINA 100 mg COMPRIMIDOS	Faes Farma S.A.	5970	COMPRIMIDO	Medicamento Sujeto A Prescripción Médica. Tratamiento De Larga Duración	Commercialized

Philippines FDA Drug Approvals

Approved Product	Company	License Number	Dosage Form	Strength	Approval Date
No Philippines FDA approvals found for this drug.

Saudi SFDA Drug Approvals

Approved Product	Company	License Number	Dosage Form	Strength	Approval Date
No Saudi SFDA approvals found for this drug.

Malaysia NPRA Drug Approvals

Approved Product	Company	Registration Number	Dosage Form	Strength	Approval Date
No Malaysia NPRA approvals found for this drug.

UK EMC Drug Information

Medicine Name	MA Holder	MA Number	Pharmaceutical Form	Active Ingredient	Authorization Date
No UK EMC drug information found for this drug.

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