What the label lists and what reports show
Tizanidine side effects
Tizanidine's FDA label: “The most common adverse reactions (greater than 10% of patients taking tizanidine and greater than in patients taking placebo) were dry mouth, somnolence, asthenia, and dizziness.” FAERS holds 41,179 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fatigue (3,191 reports).
- Generic listed
Check it at the source: the tizanidine FDA label on DailyMed (effective January 2, 2026, Legacy Pharma USA, Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (greater than 10% of patients taking tizanidine and greater than in patients taking placebo) were dry mouth, somnolence, asthenia, and dizziness.
Table 1: Multiple Dose, Placebo-Controlled Studies-Adverse Reactions Reported in >2% of Patients Treated with Zanaflex Tablets and Incidence Greater than Placebo
| Adverse Reaction | Placebo N = 261 % | Zanaflex Tablet N = 264 % |
|---|---|---|
| Dry mouth | 10 | 49 |
| Somnolence | 10 | 48 |
| Asthenia includes weakness, fatigue, and/or tiredness | 16 | 41 |
| Dizziness | 4 | 16 |
| UTI | 7 | 10 |
| Infection | 5 | 6 |
| Liver test abnormality | 2 | 6 |
| Constipation | 1 | 4 |
| Vomiting | 0 | 3 |
| Speech disorder | 0 | 3 |
| Amblyopia (blurred vision) | <1 | 3 |
| Urinary frequency | 2 | 3 |
| Flu syndrome | 2 | 3 |
| Dyskinesia | 0 | 3 |
| Nervousness | <1 | 3 |
| Pharyngitis | 1 | 3 |
| Rhinitis | 2 | 3 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described elsewhere in other sections of the prescribing information: Hypotension [see Warnings and Precautions ( 5.1 )] Liver Injury [see Warnings and Precautions ( 5.2 )] Sedation [see Warnings and Precautions ( 5.3 )] Hallucinosis/Psychotic-Like Symptoms [see Warnings and Precautions ( 5.4 )] Hypersensitivity Reactions [see Warnings and Precautions ( 5.5 )] Withdrawal Adverse Reactions [see Warnings and Precautions ( 5.6 )] The most common adverse reactions (greater than 10% of patients taking tizanidine and greater than in patients taking placebo) were dry mouth, somnolence, asthenia, and dizziness. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Legacy Pharma Inc. at 1-8007277151 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in clinical practice. The safety of Zanaflex has been evaluated in three double-blind, randomized, placebo-controlled clinical studies [see Clinical Studies ( 14 )]. Two studies were conducted in patients with multiple sclerosis and one in patients with spinal cord injury.
Source: FDA drug label, Legacy Pharma USA, Inc., effective January 2, 2026 (SPL set 60c27d35-7349-4fc6-86ad-70fffdbe3e08), via openFDA; the full label on DailyMed
What do FAERS reports show?
41,179 reports list tizanidine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 2,781 are coded as a death and 11,827 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 23 reactions below, 7 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Tizanidine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions