LAMICTAL vs PHENYTOIN SODIUM

Independent side-by-side comparison.

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

Possible drug interaction. LAMICTAL 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	LAMICTAL	PHENYTOIN SODIUM
Rating	70/100	New
Pharmacy pays	~$4.39 /30	$0.18 /mL
Type	RX	RX
Active ingredient	LAMOTRIGINE	PHENYTOIN SODIUM
Manufacturer	Glaxosmithkline	Marsam Pharms LLC
Dosage forms	Tablet, Kit	Capsule, Injectable
Drug class	Anti-Epileptic Agent	Anti-Epileptic Agent
Boxed warning	Boxed warning	None
Half-life	about 25 to 33 hours in healthy adults taking no other medications — the label reports a mean elimination half-life of 32.8 hours after a single dose (individual range 14 to 103 hours) and 25.4 hours with repeat dosing (range 11.6 to 61.6 hours), since lamotrigine induces its own metabolism	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	Bipolar Disorder, Partial Epilepsies, Seizures	Tonic-Clonic Epilepsy, Temporal Lobe Epilepsy, Status Epilepticus

lamictal phenytoin sodium

Rating

70/100

New

Pharmacy pays

~$4.39 /30

$0.18 /mL

Type

Active ingredient

LAMOTRIGINE

PHENYTOIN SODIUM

Manufacturer

Glaxosmithkline

Marsam Pharms LLC

Dosage forms

Tablet, Kit

Capsule, Injectable

Drug class

Anti-Epileptic Agent

Boxed warning

None

Half-life

about 25 to 33 hours in healthy adults taking no other medications — the label reports a mean elimination half-life of 32.8 hours after a single dose (individual range 14 to 103 hours) and 25.4 hours with repeat dosing (range 11.6 to 61.6 hours), since lamotrigine induces its own metabolism

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

Bipolar Disorder, Partial Epilepsies, Seizures

Tonic-Clonic Epilepsy, Temporal Lobe Epilepsy, Status Epilepticus

Frequently asked questions

What is the difference between Lamictal and Phenytoin Sodium?

Lamictal contains Lamotrigine, 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.