Skip to Content

Zanaflex Side Effects

Generic Name: tizanidine

Note: This page contains side effects data for the generic drug tizanidine. It is possible that some of the dosage forms included below may not apply to the brand name Zanaflex.

In Summary

Common side effects of Zanaflex include: dizziness, drowsiness, bradycardia, hypotension, weakness, fatigue, and xerostomia. Other side effects include: constipation, and increased liver enzymes. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to tizanidine: oral capsule, oral tablet

As well as its needed effects, tizanidine (the active ingredient contained in Zanaflex) may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking tizanidine, check with your doctor immediately:

More common:
  • Chest pain or discomfort
  • fever or chills
  • nausea or vomiting
  • nervousness
  • pain or burning while urinating
  • unusual tiredness
Less common:
  • Blurred vision
  • flu-like symptoms
  • irregular heartbeat
  • itching skin
  • kidney stones
  • right upper stomach tenderness
  • seeing things that are not there
  • shortness of breath
  • weight gain
Incidence not known:
  • Continuing vomiting
  • general feeling of tiredness or weakness
  • headache
  • light-colored stools

If any of the following symptoms of overdose occur while taking tizanidine, get emergency help immediately:

Symptoms of overdose:
  • Blurred vision
  • change in consciousness
  • chest pain or discomfort
  • confusion
  • decreased awareness or responsiveness
  • difficult or troubled breathing
  • dizziness, faintness or lightheadedness when getting up from a lying position
  • irregular, fast or slow, or shallow breathing
  • lightheadedness, dizziness, or fainting
  • loss of consciousness
  • pale or blue lips, fingernails, or skin
  • severe sleepiness
  • sleepiness or unusual drowsiness
  • slow or irregular heartbeat
  • sweating
  • unusual tiredness or weakness

Minor Side Effects

Some tizanidine side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common:
  • Dizziness or lightheadedness, especially when getting up from a lying or sitting position
  • drowsiness
  • dry mouth
  • fatigue
  • sleepiness
  • weakness
Less common:
  • Constipation
  • nervousness
  • sore throat

For Healthcare Professionals

Applies to tizanidine: oral capsule, oral tablet

General

The most frequently reported adverse reactions include dry mouth, somnolence/sedation, asthenia, and dizziness.[Ref]

Nervous system

Very common (10% or more): Somnolence (up to 48%), dizziness (up to 16%)
Common (1% to 10%): Speech disorder, dyskinesia
Frequency not reported: Headache, ataxia, dysarthria
Postmarketing reports: Convulsion, paresthesia, tremor[Ref]

Gastrointestinal

Very common (10% or more): Dry mouth (up to 49%)
Common (1% to 10%): Vomiting, constipation
Rare (0.01% to 0.1%): Nausea, gastrointestinal disorder
Frequency not reported: Abdominal pain, loss of appetite[Ref]

Hepatic

Common (1% to 10%): Liver test abnormality
Very rare (less than 0.01%): Hepatic failure
Frequency not reported: Hepatotoxicity
Postmarketing reports: Hepatitis[Ref]

Cardiovascular

Common (1% to 10%): Bradycardia, hypotension, tachycardia
Postmarketing reports: Syncope, ventricular tachycardia, QT prolongation[Ref]

Ocular

Common (1% to 10%): Amblyopia
Frequency not reported: Accommodation disorder[Ref]

Dermatologic

Frequency not reported: Pruritus
Postmarketing reports: Stevens Johnson Syndrome, exfoliative dermatitis, rash[Ref]

Other

Common (1% to 10%): Fatigue
Frequency not reported: Drug withdrawal reactions including rebound hypertension, tachycardia, and hypertonia[Ref]

Genitourinary

Common (1% to 10%): Urinary tract infection, urinary frequency[Ref]

Respiratory

Common (1% to 10%): Pharyngitis, rhinitis[Ref]

Hypersensitivity

Frequency not reported: Anaphylaxis, hypersensitivity reactions
Postmarketing reports: Anaphylactic Reaction[Ref]

Immunologic

Common (1% to 10%): Infection, flu syndrome[Ref]

Musculoskeletal

Rare (0.01% to 0.1%): Muscular weakness
Postmarketing reports: Arthralgia[Ref]

Psychiatric

Common (1% to 10%): Nervousness
Rare (0.01% to 0.1%): Hallucinations, insomnia, sleep disorders
Frequency not reported: Confusional state
Postmarketing reports: Depression[Ref]

References

1. "Product Information. Zanaflex (tizanidine)." Acorda Therapeutics, Hawthorne, NY.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

It is possible that some side effects of Zanaflex may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.

Hide