Two medicines, side by side
Phenytoin vs lamotrigine
Phenytoin and lamotrigine are both labeled for seizures and epilepsy. Drugs@FDA records approvals of phenytoin since 1953 and of lamotrigine since 1994. Pharmacies paid $0.145 per phenytoin sod ext 100 mg capsule and $0.0268 per lamotrigine 25 mg tablet (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. Lamotrigine's other strengths are brand-only: $2.86 per mL (Subvenite 10 mg/mL suspension). In FDA's classes, phenytoin is an anti-epileptic agent and lamotrigine a mood stabilizer.
Check it at the source: the phenytoin FDA label on DailyMed (effective October 15, 2024); the lamotrigine FDA label on DailyMed (effective October 10, 2025).
Highlights of the phenytoin record
Phenytoin (Dilantin) · label of October 15, 2024
Used for
From the label: indicationsPHENYTEK ® capsules (extended phenytoin sodium capsules) are indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. […]
On the market
- Earliest approval on file
- January 6, 1953
- Generic labelers
- 29 labelers
- Pharmacy cost
- $0.145 per capsule
Supply and safety
- Shortage
- No current entry
- Recalls
- 11
Highlights of the lamotrigine record
Lamotrigine (Lamictal) · label of October 10, 2025
SERIOUS SKIN RASHES LAMICTAL can cause serious rashes requiring hospitalization and discontinuation of treatment. The incidence of these rashes, which have included Stevens-Johnson syndrome, is approximately 0.3% to 0.8% in pediatric patients (aged 2 to 17 years) and 0.08% to 0.3% in adults receiving LAMICTAL. One rash-related death was reported in a prospectively followed cohort of 1,983 pediatric patients (aged 2 to 16 years) with epilepsy taking LAMICTAL as adjunctive therapy.
Used for
From the label: indicationsLAMICTAL is indicated for: Epilepsy–adjunctive therapy in patients aged 2 years and older: • partial-onset seizures. • primary generalized tonic-clonic (PGTC) seizures. • generalized seizures of Lennox-Gastaut syndrome. […]
On the market
- Earliest approval on file
- December 27, 1994
- Generic labelers
- 49 labelers
- Pharmacy cost
- $0.0268 per tablet
Supply and safety
- Shortage
- A presentation being discontinued
- Recalls
- 10
Source: FDA drug labels via openFDA (Phenytoin label of October 15, 2024, Lamotrigine label of October 10, 2025); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do phenytoin and lamotrigine differ on the record?
In FDA's classes, phenytoin is an anti-epileptic agent and lamotrigine a mood stabilizer.
How each works, in its label's words: Phenytoin, “The precise mechanism by which phenytoin exerts its therapeutic effect has not been established but is thought to involve the voltage-dependent blockade of membrane sodium channels resulting in a …”; Lamotrigine, “The precise mechanism(s) by which lamotrigine exerts its anticonvulsant action are unknown.”
Only the lamotrigine label carries a boxed warning.
Generics: phenytoin since 1975; lamotrigine since 2006 (Drugs@FDA).
| Phenytoin | Lamotrigine | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Seizures and epilepsy, Bipolar disorder |
| Pharmacologic class | Anti-epileptic Agent | Anti-epileptic Agent, Mood Stabilizer |
| How it works (label) | The precise mechanism by which phenytoin exerts its therapeutic effect has not been established but is thought to involve the voltage-dependent blockade of membrane sodium channels resulting in a reduction in sustained high-frequency … | The precise mechanism(s) by which lamotrigine exerts its anticonvulsant action are unknown. |
| Half-life (label) | Elimination The plasma half-life in man after oral administration of phenytoin averages 22 hours, with a range of 7 to 42 hours. | n/a |
| Earliest approval on file (Drugs@FDA) | January 6, 1953 | December 27, 1994 |
| First generic approved | July 16, 1975 | June 21, 2006 |
| Generic labelers (NDC) | 29 labelers | 49 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.145 per capsule (Phenytoin sod ext 100 mg capsule) | $0.0268 per tablet (Lamotrigine 25 mg tablet) |
| 12-month price change | -5% | -12% |
| Boxed warning | No | Yes |
| Shortage now | No current entry | A presentation being discontinued |
| Recalls recorded | 11 | 10 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 40,278 | 130,994 |
| DEA schedule | none | none |
Source: Drugs@FDA, FDA NDC Directory, CMS NADAC of October 7, 2026, FDA shortages and recalls, FAERS via openFDA (FDA files October 8, 2026)
Do their labels mention each other?
Phenytoin label, drug interactionsInteracting Agent: Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable; Examples: Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide
Lamotrigine label, drug interactionsConcomitant Drug: Phenytoin; Effect on Concentration of Lamotrigine or Concomitant Drug: ↓ lamotrigine; Clinical Comment: Decreased lamotrigine concentration approximately 40%.
Lamotrigine label, drug interactionsDRUG INTERACTIONS Valproate increases lamotrigine concentrations more than 2-fold. ( 7 , 12.3 ) Carbamazepine, phenytoin, phenobarbital, primidone, and rifampin decrease lamotrigine concentrations by approximately 40%. ( 7 , 12.3 ) Estrogen-containing oral contraceptives decrease lamotrigine concentrations by approximately 50%. …
Source: FDA drug labels via openFDA
What next?
- Alternatives to phenytoin
- every medicine labeled for the same conditions