Zanaflex Side Effects

Generic name: tizanidine

Medically reviewed by Drugs.com. Last updated on Aug 15, 2023.

Note: This document contains side effect information about tizanidine. Some dosage forms listed on this page may not apply to the brand name Zanaflex.

Applies to tizanidine: oral capsule, oral tablet.

Serious side effects of Zanaflex

Along with its needed effects, tizanidine (the active ingredient contained in Zanaflex) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking tizanidine:

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

Get emergency help immediately if any of the following symptoms of overdose occur while taking tizanidine:

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

Other side effects of Zanaflex

Some side effects of tizanidine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions 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]

Frequently asked questions

• What is Miderizone used for?

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer