Tizanidine: Muscle Relaxer Uses, Warnings, Side Effects, Dosage

Generic Name: tizanidine

Brand Name: Zanaflex

Drug Class: Alpha2 adrenergic agonists

What is tizanidine, and what is it used for?

Tizanidine is a medication used in the management of muscle spasticity, a condition with high muscle tone and stiffness that leads to pain and impaired mobility.

Muscle spasticity is a neuromuscular disorder that causes uncontrolled and prolonged contraction of muscles because of disrupted signals between the nerves and muscles. Tizanidine is effective for muscle spasticity caused by conditions such as multiple sclerosis, and brain, spinal cord or musculoskeletal injuries, all of which can damage nerves.

Tizanidine belongs to a class of medications known as alpha2 adrenergic agonists. Tizanidine acts on the central nervous system to produce muscle relaxation. Tizanidine stimulates alpha2 adrenergic receptors, protein molecules on nerve cells (neurons), and inhibits the motor neurons from releasing excitatory chemicals (neurotransmitters) such as glutamate and aspartate that are responsible for sending signals to the muscles to contract.

Tizanidine is approved by the FDA to treat muscle spasticity in adults. The off-label uses of tizanidine in adults include:

Chronic neck and/or lower back pain
Chronic migraine headaches
Rebound headaches due to analgesic withdrawal
Regional musculoskeletal pain syndromes
Refractory insomnia in spastic quadriplegic patients

Warnings

Do not use in patients with hypersensitivity to tizanidine or any of its components
Do not use tizanidine concurrently with ciprofloxacin, fluvoxamine or other potent CYP1A2 inhibiting drugs, can increase tizanidine concentration and effects.
Concurrent use with CYP1A2 inducers can decrease tizanidine levels.
Oral contraceptives can decrease tizanidine clearance, use with caution.
Tizanidine can cause hypotension, orthostatic hypotension and syncope. Titrate dose with caution and monitor patients for symptoms.
Tizanidine can cause liver injury, use with caution in patients with impaired liver function and monitor liver enzymes before and after therapy.
Use tizanidine with caution in patients with renal impairment.
Use with caution in geriatric patients.
Tizanidine can cause sedation. Avoid concurrent use with other central nervous system (CNS) depressant drugs such as benzodiazepines and opioids, can have additive effect.
Visual hallucinations and psychosis-like reactions can occur. If a patient develops such reactions, discontinue tizanidine.
Tizanidine can cause severe hypersensitivity reactions including anaphylaxis and severe skin reactions such as Stevens-Johnson syndrome and exfoliative dermatitis. Discontinue the drug immediately in case of hypersensitivity.
Abrupt discontinuation can cause rebound hypertension, tachycardia and hypertonia. Withdraw tizanidine gradually to reduce the risk of withdrawal symptoms.

What are the side effects of tizanidine?

Common side effects of tizanidine include:

Drowsiness (somnolence)
Dry mouth (xerostomia)
Weakness or/and fatigue (asthenia)
Dizziness
Slow heart rate (bradycardia)
Low blood pressure (hypotension)
Urinary tract infection
Infections
Constipation
Liver injury
Elevated liver enzymes, particularly, alanine aminotransferase (ALT)

Less common side effects of tizanidine include:

Vomiting
Urinary frequency
Flu syndrome
Nasal inflammation (rhinitis)
Throat inflammation (pharyngitis)
Blurred vision
Speech disorder
Movement disorder (dyskinesia)
Nervousness
Sedation
Hallucination
Delusion
Withdrawal symptoms upon discontinuation include:
- Rapid heart rate (tachycardia)
- High blood pressure (hypertension)
- Increased spasticity (hypertonia)
Rare side effects of tizanidine include:
- Severe skin reactions including:
  - Rash
  - Stevens-Johnson syndrome
  - Exfoliative dermatitis
Severe allergic reaction (anaphylaxis)
Ventricular tachycardia
Drop in blood pressure when standing up from sitting or lying down (orthostatic hypotension)
Fainting (syncope)
Liver inflammation (hepatitis)
Convulsion
Depression
Joint pain (arthralgia)
Abnormal skin sensations (paresthesia)
Tremor

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

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What are the dosages of tizanidine?

Tablet

2 mg
4 mg

Capsule

2 mg
4 mg
6 mg

Adult:

Muscle Spasticity

Spasticity associated with multiple sclerosis and spinal cord injury

Initial: 2 mg orally every 6-8 hours as needed; no more than 3 doses every 24 hours
Maintenance: Titrate in 2-4 mg/day increments to optimum effect with minimum 1-4 days between dose increments
Not to exceed 36 mg/day; single doses greater than 16 mg not studied
To discontinue taper gradually; decrease by 2-4 mg daily

Dosing Modifications

Renal impairment

Creatinine clearance (CrCl) less than 25 mL/minute: Use caution; clearance reduced greater than 50%
CrCl greater than 25 mL/minute: Not studied; use caution

Hepatic impairment

Close monitoring of adverse drug reactions (ADRs) (e.g., hypotension); avoid in severe impairment

Pediatric:

Not recommended

Overdose

Tizanidine overdose can cause lethargy, drowsiness, confusion, respiratory and cardiac depression, coma, and death.
Overdose is treated with supportive and symptomatic care, including monitoring of respiratory and cardiac functions. Symptoms of overdose generally resolve within three days after discontinuation of tizanidine.

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Nearly everyone has low back pain at some time during their life.
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What drugs interact with tizanidine?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

Tizanidine has no known severe interactions with other drugs.
Tizanidine has serious interactions with at least 35 different drugs.
Tizanidine has moderate interactions with at least 35 different drugs.
Tizanidine has mild interactions with at least 79 different drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

Pregnancy and breastfeeding

There are no adequate and well-controlled studies on the safety of tizanidine use in pregnant women. Tizanidine should be used during pregnancy only if benefits from the drug justify potential risks to the fetus.
It is not known if tizanidine is present in breast milk. Use tizanidine with caution in nursing mothers because many drugs are excreted in breast milk.

What else should I know about tizanidine?

Take tizanidine exactly as prescribed. Do not switch between tablets and capsules and do not discontinue abruptly, it can cause rebound hypertension and tachycardia.
Keep tizanidine safely out of reach of children.
In case of overdose, seek immediate medical help or contact Poison Control Center.
Avoid alcohol while on tizanidine therapy; it can have additive effects.
Avoid activities such as driving or operating heavy machinery while taking tizanidine until it is clear that the drug does not make you dizzy or drowsy.