tizanidine
Brand names: Zanaflex
Tizanidine is a muscle relaxant. It is used to treat spasticity, which is when your muscles are tight or stiff.
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.
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.
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.
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.
Storage
Store tizanidine at room temperature, away from light and moisture.
Side Effects (from patient reports)
Based on 13,125 FDA adverse event reports.
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
Death-Related Reports
1,739
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 |
| 3 | DRUG INEFFECTIVE | 1,572 |
| 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 |
| 10 | OFF LABEL USE | 945 |
| 11 | ARTHRALGIA | 814 |
| 12 | ACUTE KIDNEY INJURY | 808 |
| 13 | VOMITING | 792 |
| 14 | ASTHENIA | 778 |
| 15 | ANXIETY | 773 |
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.
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
Related Medications in Central Alpha-2 Agonist (Muscle Relaxant)
Other drugs grouped near tizanidine — same-class peers and common alternatives.
baclofen
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carisoprodol
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chlorzoxazone
Parafon Forte
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cyclobenzaprine
Flexeril, Amrix
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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
Related Health & Safety Data
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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 13,125 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.
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