PHENYTOIN SODIUM vs VALPROATE SODIUM

Independent side-by-side comparison.

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

Possible drug interaction. PHENYTOIN SODIUM and VALPROATE 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	PHENYTOIN SODIUM	VALPROATE SODIUM
Rating	New	70/100
Pharmacy pays	$0.18 /mL	—
Type	RX	RX
Active ingredient	PHENYTOIN SODIUM	VALPROATE SODIUM
Manufacturer	Marsam Pharms LLC	Sagent
Dosage forms	Capsule, Injectable	Injectable, Solution
Drug class	Anti-Epileptic Agent	Anti-Epileptic Agent
Boxed warning	None	Boxed warning
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.	about 9 to 16 hours (the label's mean terminal, or elimination, half-life for valproate monotherapy after oral doses of 250 to 1,000 mg)
Treats	Tonic-Clonic Epilepsy, Temporal Lobe Epilepsy, Status Epilepticus	—

phenytoin sodium valproate sodium

Rating

New

70/100

Pharmacy pays

$0.18 /mL

—

Type

Active ingredient

PHENYTOIN SODIUM

VALPROATE SODIUM

Manufacturer

Marsam Pharms LLC

Sagent

Dosage forms

Capsule, Injectable

Injectable, Solution

Drug class

Anti-Epileptic Agent

Boxed warning

None

Boxed warning

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.

about 9 to 16 hours (the label's mean terminal, or elimination, half-life for valproate monotherapy after oral doses of 250 to 1,000 mg)

Treats

Tonic-Clonic Epilepsy, Temporal Lobe Epilepsy, Status Epilepticus

—

Frequently asked questions

What is the difference between Phenytoin Sodium and Valproate Sodium?

Phenytoin Sodium contains Phenytoin Sodium, while Valproate Sodium contains Valproate 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.