tizanidine Side Effects
Also known as: Zanaflex
Analysis of 22,750 adverse event reports submitted to the FDA from 2004 to 2025.
Total Reports
22,750
Death-Related
1,739
7.6% of reports
Hospitalizations
6,474
28.5% 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 1,739 reports where death was an outcome. These are voluntarily reported and do not establish causation.
| Reaction | Reports |
|---|---|
| DEATH | 499 |
| COMPLETED SUICIDE | 485 |
| TOXICITY TO VARIOUS AGENTS | 274 |
| CARDIO-RESPIRATORY ARREST | 129 |
| CARDIAC ARREST | 108 |
| SUSPECTED SUICIDE | 106 |
| ACUTE KIDNEY INJURY | 100 |
| CHRONIC KIDNEY DISEASE | 98 |
| RENAL FAILURE | 76 |
| RESPIRATORY ARREST | 72 |
| END STAGE RENAL DISEASE | 56 |
| PNEUMONIA | 47 |
| FALL | 44 |
| OFF LABEL USE | 38 |
| OVERDOSE | 38 |
| SEPTIC SHOCK | 36 |
| HYPOTENSION | 34 |
| ASTHENIA | 30 |
| DYSPNOEA | 29 |
| URINARY TRACT INFECTION | 29 |
Reactions in Hospitalization Reports
Top reactions in 6,474 reports where hospitalization was an outcome.
| Reaction | Reports |
|---|---|
| FALL | 598 |
| PAIN | 484 |
| NAUSEA | 480 |
| PNEUMONIA | 452 |
| URINARY TRACT INFECTION | 428 |
| FATIGUE | 424 |
| DYSPNOEA | 348 |
| ACUTE KIDNEY INJURY | 338 |
| HEADACHE | 337 |
| VOMITING | 337 |
| ASTHENIA | 325 |
| DIARRHOEA | 323 |
| HYPOTENSION | 323 |
| DIZZINESS | 299 |
| SOMNOLENCE | 299 |
| DRUG INEFFECTIVE | 258 |
| ARTHRALGIA | 257 |
| OFF LABEL USE | 256 |
| MULTIPLE SCLEROSIS RELAPSE | 252 |
| CHRONIC KIDNEY DISEASE | 248 |
Nearby — Related Medications
What the FAERS Data Reveals About tizanidine Side Effects
The FDA Adverse Event Reporting System (FAERS) contains 22,750 voluntary reports linked to tizanidine and its brand equivalents (Zanaflex), spanning 2004 through 2025. Of those, 1,739 (7.6%) listed death as an outcome and 6,474 (28.5%) 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, 75% were female and 25% male; age distribution skews toward 45-64, with 7,737 reports in that bracket. The single most reported reaction is fatigue with 1,693 submissions, followed by pain and drug ineffective.
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.