FOSPHENYTOIN SODIUM vs PHENYTOIN SODIUM

Independent side-by-side comparison.

Rated against independent regulatory sources·Last updated August 21, 2026·How we rate

Possible drug interaction. FOSPHENYTOIN SODIUM and PHENYTOIN SODIUM are different prescription medicines. Combining or switching between them can cause interactions — talk to a pharmacist or prescriber before making changes. This page is not medical advice.

Attribute	FOSPHENYTOIN SODIUM	PHENYTOIN SODIUM
Rating	72/100	New
Pharmacy pays	—	$0.18 /mL
Type	RX	RX
Active ingredient	FOSPHENYTOIN SODIUM	PHENYTOIN SODIUM
Manufacturer	Hikma	Marsam Pharms LLC
Dosage forms	Injectable, Solution	Capsule, Injectable
Drug class	Anti-Epileptic Agent	Anti-Epileptic Agent
Boxed warning	Boxed warning	None
Half-life	—	About 22 hours on average, ranging from 7 to 42 hours — but phenytoin does NOT have a single fixed half-life. It follows nonlinear, saturable (Michaelis-Menten) kinetics, so the half-life lengthens as the dose and blood level rise; the label warns that "small incremental doses may increase the half-life and produce very substantial increases in serum levels" once levels are in the upper range.
Treats	Seizures, Status Epilepticus	Tonic-Clonic Epilepsy, Temporal Lobe Epilepsy, Status Epilepticus

fosphenytoin sodium phenytoin sodium

Rating

72/100

New

Pharmacy pays

—

$0.18 /mL

Type

Active ingredient

FOSPHENYTOIN SODIUM

PHENYTOIN SODIUM

Manufacturer

Hikma

Marsam Pharms LLC

Dosage forms

Injectable, Solution

Capsule, Injectable

Drug class

Anti-Epileptic Agent

Boxed warning

None

Half-life

—

About 22 hours on average, ranging from 7 to 42 hours — but phenytoin does NOT have a single fixed half-life. It follows nonlinear, saturable (Michaelis-Menten) kinetics, so the half-life lengthens as the dose and blood level rise; the label warns that "small incremental doses may increase the half-life and produce very substantial increases in serum levels" once levels are in the upper range.

Treats

Seizures, Status Epilepticus

Tonic-Clonic Epilepsy, Temporal Lobe Epilepsy, Status Epilepticus

Frequently asked questions

What is the difference between Fosphenytoin Sodium and Phenytoin Sodium?

Fosphenytoin Sodium contains Fosphenytoin Sodium, while Phenytoin Sodium contains Phenytoin Sodium — they have different active ingredients.

Ratings are based on FDA regulatory (recall-safety) data. This comparison is for general reference only — not medical advice. Always consult a licensed professional before choosing or switching a medication.