phenytoin Side Effects
Also known as: Dilantin
Analysis of 20,453 adverse event reports submitted to the FDA from 2004 to 2025.
Total Reports
20,453
Death-Related
2,949
14.4% of reports
Hospitalizations
8,381
41.0% of reports
Top Indication
Product Used For Unknown Indication
Most Reported Adverse Reactions
Who Reports Side Effects
Gender Distribution
Age Distribution
Reporting Trend by Year
Reactions in Death Reports
Top reactions reported in 2,949 reports where death was an outcome. These are voluntarily reported and do not establish causation.
| Reaction | Reports |
|---|---|
| DEATH | 364 |
| COMPLETED SUICIDE | 358 |
| DRUG INEFFECTIVE | 290 |
| CARDIAC ARREST | 237 |
| TOXICITY TO VARIOUS AGENTS | 236 |
| SEPSIS | 202 |
| OFF LABEL USE | 186 |
| STATUS EPILEPTICUS | 137 |
| DRUG INTERACTION | 130 |
| TOXIC EPIDERMAL NECROLYSIS | 130 |
| PNEUMONIA | 126 |
| HYPOTENSION | 120 |
| STEVENS-JOHNSON SYNDROME | 111 |
| RENAL FAILURE | 103 |
| RESPIRATORY FAILURE | 101 |
| MULTIPLE ORGAN DYSFUNCTION SYNDROME | 99 |
| CONVULSION | 96 |
| BRAIN OEDEMA | 89 |
| THROMBOCYTOPENIA | 89 |
| PYREXIA | 88 |
Reactions in Hospitalization Reports
Top reactions in 8,381 reports where hospitalization was an outcome.
| Reaction | Reports |
|---|---|
| DRUG INEFFECTIVE | 1,183 |
| DRUG INTERACTION | 848 |
| TOXICITY TO VARIOUS AGENTS | 813 |
| SEIZURE | 532 |
| OFF LABEL USE | 491 |
| CONVULSION | 468 |
| PYREXIA | 467 |
| STATUS EPILEPTICUS | 446 |
| STEVENS-JOHNSON SYNDROME | 430 |
| FALL | 413 |
| DRUG REACTION WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS | 390 |
| CONFUSIONAL STATE | 366 |
| VOMITING | 327 |
| ATAXIA | 326 |
| HYPOTENSION | 308 |
| DIZZINESS | 298 |
| NAUSEA | 293 |
| SOMNOLENCE | 279 |
| NYSTAGMUS | 274 |
| PNEUMONIA | 265 |
Nearby — Related Medications
What the FAERS Data Reveals About phenytoin Side Effects
The FDA Adverse Event Reporting System (FAERS) contains 20,453 voluntary reports linked to phenytoin and its brand equivalents (Dilantin), spanning 2004 through 2025. Of those, 2,949 (14.4%) listed death as an outcome and 8,381 (41.0%) involved hospitalization. The most common indication reported alongside adverse events was Product Used For Unknown Indication.
Demographic breakdowns help contextualize who is being exposed to the drug. Of reports with known sex, 48% were female and 51% male; age distribution skews toward 18-44, with 4,572 reports in that bracket. The single most reported reaction is drug ineffective with 2,670 submissions, followed by drug interaction and seizure.
FAERS is a signal-detection tool, not a scorecard. Reports are voluntary, and a single case may list multiple suspect drugs, so numbers above should not be read as incidence rates or per-patient risk. Widely prescribed drugs naturally accumulate more reports than niche therapies even when individual risk is low. These aggregates are useful for spotting patterns that merit further pharmacovigilance, not for choosing between medications. This page is for educational reference only and is not medical advice — speak with a licensed clinician about any side-effect concerns.
Read our methodology — how this data is sourced, computed, and verified.