Prescription medication · Central Alpha-2 Agonist (Muscle Relaxant)
tizanidine
Also sold as Zanaflex. Tizanidine is used to treat spasticity in adults.
Data updated 2026-05-15
- 22,750
- FDA reportsModerately reported
- 17
- InteractionsSeveral interactions
- 1
- Recall record
What the data shows
tizanidine (Zanaflex) is a prescription Central Alpha-2 Agonist (Muscle Relaxant), reported at a middle-of-the-pack volume (22,750 FDA reports), with 17 documented drug interactions.
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
tizanidine (Zanaflex) is a prescription Central Alpha-2 Agonist (Muscle Relaxant). Tizanidine is used to treat spasticity in adults.
Tizanidine is a muscle relaxant. It is used to treat spasticity, which is when your muscles are tight or stiff.
Verify with FDA → · CMS NADAC pricing →
Drug Pricing (NADAC)
Generic Price
$0.08/unit
Generic Available
Yes (14 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Tizanidine is used to treat spasticity in adults.
Common side effects
Dry mouth, Sleepiness, Weakness
Key warnings
Tizanidine can cause low blood pressure, liver problems, and hallucinations.
The sections below are summarized in plain English from tizanidine's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Tizanidine works by affecting certain chemicals in your brain. It is an alpha-2 adrenergic agonist. This action helps to reduce muscle spasms and tightness.
How to Take It
Take tizanidine every 6 to 8 hours as needed. Do not take more than 3 doses in 24 hours. You can take it with or without food, but be consistent. Your doctor may increase your dose every 1 to 4 days by 2 to 4 mg.
This is a plain-language summary of tizanidine's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
Tizanidine may harm your unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is not known if tizanidine passes into breast milk, so talk to your doctor if you are breastfeeding.
This is a plain-language summary of tizanidine's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
This is a plain-language summary of tizanidine's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store tizanidine at room temperature, away from light and moisture.
Side Effects (from patient reports)
Based on 22,750 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for tizanidine, by number of reports
- Tiredness
Tiredness
1,693 reports
- Aches
Aches
1,615 reports
- Feeling sick to your stomach
Feeling sick to your stomach
1,530 reports
- Falling down
Falling down
1,318 reports
- Head pain
Head pain
1,289 reports
- Long-term kidney problems
Long-term kidney problems
1,110 reports
- Loose stool
Loose stool
1,067 reports
- Feeling unsteady
Feeling unsteady
986 reports
- Joint pain
Joint pain
814 reports
- Sudden kidney damage
Sudden kidney damage
808 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for tizanidine each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where tizanidine sits
tizanidine has more FDA adverse-event reports than 57% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is tizanidine; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 22,750 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
22,750
Reports Mentioning Death
1,739
7.6% of reports — not proof of cause
Hospitalization Reports
6,474
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | FATIGUE | 1,693 |
| 2 | PAIN | 1,614 |
| 4 | NAUSEA | 1,529 |
| 5 | FALL | 1,318 |
| 6 | HEADACHE | 1,289 |
| 7 | CHRONIC KIDNEY DISEASE | 1,110 |
| 8 | DIARRHOEA | 1,066 |
| 9 | DIZZINESS | 986 |
| 11 | ARTHRALGIA | 814 |
| 12 | ACUTE KIDNEY INJURY | 808 |
| 13 | VOMITING | 792 |
| 14 | ASTHENIA | 778 |
| 15 | ANXIETY | 773 |
| 16 | DYSPNOEA | 756 |
| 17 | GAIT DISTURBANCE | 755 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Tizanidine can cause low blood pressure, liver problems, and hallucinations. It can also make you very sleepy, especially if you drink alcohol or take other medicines that cause sleepiness. Your doctor should check your liver function before you start taking tizanidine and one month after you reach your highest dose. Do not stop taking tizanidine suddenly, as this can cause withdrawal symptoms.
Known Drug Interactions
( 7.2 , 12.3 ) 7.1 Strong CYP1A2 Inhibitors Concomitant use of tizanidine with strong cytochrome P450 1A2 (CYP1A2) inhibitors (e.g., fluvoxamine, ciprofloxacin) is contraindicated.
Mechanism: Ciprofloxacin stops the body from breaking down tizanidine. This can cause tizanidine to build up to dangerous levels in your system.
What to do: Do not take these two medicines together. Ask your doctor for a different antibiotic or muscle relaxer.
( 7.2 , 12.3 ) 7.1 Strong CYP1A2 Inhibitors Concomitant use of tizanidine with strong cytochrome P450 1A2 (CYP1A2) inhibitors (e.g., fluvoxamine, ciprofloxacin) is contraindicated.
Mechanism: Fluvoxamine blocks the enzyme that normally clears tizanidine from your body. This leads to much higher amounts of tizanidine in your blood than intended.
What to do: This combination should not be used. Your doctor will need to change one of your medications to a safer option.
( 7.1 ) • Tizanidine (CYP1A2) Substrate: Potential for substantial increases in blood concentrations of tizanidine resulting in hypotension, bradycardia or excessive drowsiness; avoid concomitant use, if possible. 7.2 Tizanidine (CYP1A2 Substrate) Although not studied clinically, famotidine is considered a weak CYP1A2 inhibitor and may lead to substantial increases in blood concentrations of tizanidine, a CYP1A2 substrate. Refer to the full prescribing information for tizanidine.
Mechanism: Famotidine can slow down the body's ability to clear tizanidine, which may lead to dangerously high levels of the drug in your blood.
What to do: Avoid taking these two drugs together if possible to prevent side effects like very low blood pressure or extreme drowsiness.
7.2 Moderate or Weak CYP1A2 Inhibitors Concomitant use of tizanidine with moderate or weak CYP1A2 inhibitors (e.g., zileuton, antiarrhythmics [amiodarone, mexiletine, propafenone, and verapamil], cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine) should be avoided.
Mechanism: Acyclovir blocks a specific liver enzyme that breaks down tizanidine. This causes the muscle relaxant to stay in your body at much higher levels, which can be dangerous.
What to do: You should avoid taking these two medications together to prevent serious side effects.
7.2 Moderate or Weak CYP1A2 Inhibitors Concomitant use of tizanidine with moderate or weak CYP1A2 inhibitors (e.g., zileuton, antiarrhythmics [amiodarone, mexiletine, propafenone, and verapamil], cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine) should be avoided.
Mechanism: Verapamil slows down the liver process that clears tizanidine from your body, which can lead to higher drug levels.
What to do: You should avoid taking these two medications at the same time.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
Can I drink alcohol while taking tizanidine?
What should I do if I feel dizzy after taking tizanidine?
Can I drive while taking tizanidine?
Will tizanidine cure my spasticity?
How long does it take for tizanidine to start working?
Can I take tizanidine with other medicines?
What happens if I take too much tizanidine?
How will I know if tizanidine is working?
Can I switch between the tablet and capsule forms of tizanidine?
What tests will my doctor do while I'm taking tizanidine?
What are the common side effects of tizanidine?
Does tizanidine interact with other medications?
What drug class is tizanidine?
Is tizanidine safe during pregnancy?
Has tizanidine been recalled?
Active Recalls
Failed dissolution specification: Out of specification results observed in 24-month long term stability testing.
Dr Reddy's Laboratories Limited
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Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for tizanidine
The FDA label for tizanidine (sold under brand names such as Zanaflex) classifies it as a prescription-only medication in the Central Alpha-2 Agonist (Muscle Relaxant) class. Tizanidine is used to treat spasticity in adults. Official labeling lists 4 commonly reported side effects, including Dry mouth, Sleepiness, Weakness.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 22,750 voluntary reports. The database also lists 17 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.08.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history (currently 1 recall record on file), and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: March 11, 2025
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages