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What is Zanaflex (tizanidine)?
Zanaflex (tizanidine) is a skeletal muscle relaxant used to treat and manage skeletal muscle spasticity. Spasticity may be due to multiple sclerosis or spinal cord injury. Zanaflex works on alpha 2 receptors in the central nervous system (brain and spinal cord) and blocks nerve impulses from reaching muscles which produces muscle relaxation.
Common side effects of Zanaflex include:
- low blood pressure (hypotension),
- dry mouth,
- blurred vision, and
Serious side effects of Zanaflex include:
Drug interactions of Zanaflex include ciprofloxacin, amiodarone, cimetidine, oral contraceptives, acyclovir, and fluvoxamine, which can slow the breakdown of Zanaflex and lead to increased sedation, drowsiness, and slowed reflexes.
Zanaflex should be used with caution with medications like alprazolam, clonazepam, diazepam, zolpidem, oxycodone, hydromorphone, amitriptyline, nortriptyline, and alcohol, because they can further increase the side effects of Zanaflex.
There are no adequate studies done on Zanaflex to determine safe and effective use in pregnant women.
Zanaflex (tizanidine) side effects list for healthcare professionals
The following adverse reactions are described elsewhere in other sections of the prescribing information:
Clinical Trials Experience
Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in clinical practice.
Three double-blind, randomized, placebo controlled -clinical studies were conducted to evaluate the effect of tizanidine on spasticity control. Two studies were conducted in patients with multiple sclerosis and one in patients with spinal cord injury.
Each study had a 13-week active treatment period which included a 3-week titration phase to the maximum tolerated dose up to 36 mg/day in three divided doses, a 9-week plateau phase where the dose of tizanidine was held constant and a 1- week dose tapering. In all, 264 patients received tizanidine and 261 patients received placebo. Across the three studies patient ages ranged from 15–69 years and 51.4 percent were women. The median dose during the plateau phase ranged from 20–28 mg/day.
The most frequent adverse reactions reported in multiple dose, placebo-controlled clinical studies involving 264 patients with spasticity were dry mouth, somnolence/sedation, asthenia (weakness, fatigue and/or tiredness) and dizziness. Three-quarters of the patients rated the events as mild to moderate and one-quarter of the patients rated the events as being severe. These events appeared to be dose related.
Table 1 lists signs and symptoms that were reported in greater than 2% of patients in three multiple dose, placebo-controlled studies who received Zanaflex where the frequency in the Zanaflex group was greater than the placebo group. For comparison purposes, the corresponding frequency of the event (per 100 patients) among placebo treated patients is also provided.
Table 1: Multiple Dose, Placebo-Controlled Studies—Frequent ( > 2%) Adverse Reactions Reported for Which Zanaflex Tablets Incidence is Greater than Placebo
N = 261
N = 264
|Liver test abnormality||2||6|
|Amblyopia (blurred vision)||< 1||3|
|*(weakness, fatigue, and/or tiredness)|
In the single dose, placebo-controlled study involving 142 patients with spasticity due to multiple sclerosis (Study 1), the patients were specifically asked if they had experienced any of the four most common adverse reactions: dry mouth, somnolence (drowsiness), asthenia (weakness, fatigue and/or tiredness) and dizziness. In addition, hypotension and bradycardia were observed. The occurrence of these reactions is summarized in Table 2. Other events were, in general, reported at a rate of 2% or less.
Table 2: Single Dose, Placebo-Controlled Study—Common Adverse Reactions Reported
N = 48
|Zanaflex Tablet, 8mg,|
N = 45
|Zanaflex Tablet, 16 mg,|
N = 49
|*(weakness, fatigue, and/or tiredness)|
The following adverse reactions have been identified during post approval use of Zanaflex. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Certain events, such as somnolence, dry mouth, hypotension, decreased blood pressure, bradycardia, dizziness, weakness or asthenia, muscle spasms, hallucinations, fatigue, liver function test abnormality and hepatotoxicity, have been observed in post marketing and clinical trials and are discussed in previous sections of this document.
The following adverse reactions have been identified as occurring in the post marketing experience of Zanaflex. Based on the information provided regarding these reactions, a causal relationship with Zanaflex cannot be entirely excluded. The events are listed in order of decreasing clinical significance; severity in the post marketing setting is not reported.
What drugs interact with Zanaflex (tizanidine)?
Concomitant use of fluvoxamine and Zanaflex is contraindicated. Changes in pharmacokinetics of tizanidine when administered with fluvoxamine resulted in significantly decreased blood pressure, increased drowsiness, and increased psychomotor impairment.
Concomitant use of ciprofoxacin and Zanaflex is contraindicated. Changes in pharmacokinetics of tizanidine when administered with ciprofloxacin resulted in significantly decreased blood pressure, increased drowsiness, and increased psychomotor impairment.
CYP1A2 Inhibitors other than Fluvoxamine and Ciprofloxacin
Because of potential drug interactions, concomitant use of Zanaflex with other CYP1A2 inhibitors, such as zileuton, fluoroquinolones other than strong CYP1A2 inhibitors (which are contraindicated), antiarrythmics (amiodarone, mexiletine, propafenone, and verapamil), cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine) should be avoided. If their use is clinically necessary, therapy should be initiated with 2 mg dose and increased in 2–4 mg steps daily based on patient response to therapy. If adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce or discontinue Zanaflex therapy.
Concomitant use of Zanaflex with oral contraceptives is not recommended. However, if concomitant use is clinically necessary, initiate Zanaflex with a single 2 mg dose and increase in 2–4 mg steps daily based on patient response to therapy. If adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce or discontinue Zanaflex therapy.
Alcohol increases the overall amount of drug in the bloodstream after a dose of Zanaflex. This was associated with an increase in adverse reactions of Zanaflex. The CNS depressant effects of Zanaflex and alcohol are additive.
Other CNS Depressants
The sedative effects of Zanaflex with CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants) may be additive. Monitor patients who take Zanaflex with another CNS depressant for symptoms of excess sedation.
Because hypotensive effects may be cumulative, it is not recommended that Zanaflex be used with other a2-adrenergic agonists.
Drug Abuse And Dependence
Abuse potential was not evaluated in human studies. Rats were able to distinguish tizanidine from saline in a standard discrimination paradigm, after training, but failed to generalize the effects of morphine, cocaine, diazepam, or phenobarbital to tizanidine.
Tizanidine is closely related to clonidine, which is often abused in combination with narcotics and is known to cause symptoms of rebound upon abrupt withdrawal. Three cases of rebound symptoms on sudden withdrawal of tizanidine have been reported. The case reports suggest that these patients were also misusing narcotics.
Withdrawal symptoms included hypertension, tachycardia, hypertonia, tremor, and anxiety. Withdrawal symptoms are more likely to occur in cases where high doses are used, especially for prolonged periods, or with concomitant use of narcotics. If therapy needs to be discontinued, the dose should be decreased slowly to minimize the risk of withdrawal symptoms.
Monkeys were shown to self-administer tizanidine in a dose-dependent manner, and abrupt cessation of tizanidine produced transient signs of withdrawal at doses > 35 times the maximum recommended human dose on a mg/m² basis. These transient withdrawal signs (increased locomotion, body twitching, and aversive behavior toward the observer) were not reversed by naloxone administration.
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Spinal Cord Injury: Treatments and Rehabilitation
When vertebrae are broken or dislocated, the result can cause traumatic injury to the spinal cord. A spinal cord injury can have significant physiological consequences. One indication of the severity of a spinal cord injury are respiratory complications. Spinal cord injuries are classified as either. Rehabilitation and recovery of a spinal cord injury is dependant upon the type of injury.
Multiple Sclerosis (MS)
Multiple sclerosis or MS is an autoimmune disorder in which brain and spinal cord nerve cells become demyelinated. This damage results in symptoms that may include numbness, weakness, vertigo, paralysis, and involuntary muscle contractions. Different forms of MS can follow variable courses from relatively benign to life-threatening. MS is treated with disease-modifying therapies. Some MS symptoms can be treated with medications.
MS (Multiple Sclerosis) vs. ALS (Amyotrophic Lateral Sclerosis) Differences and Similarities
ALS (amyotrophic lateral sclerosis, Lou Gehrig's disease) and MS (multiple sclerosis) are both diseases of the nervous system (neurodegenerative). ALS is a disease in which the nerve cells in the body are attacked by the immune system, although it's not considered an autoimmune disease by some scientists. MS is an autoimmune disease in which the insulated covering of the nerves (myelin sheath) in the CNS (central nervous system) degenerate, or deteriorate. Scientists don't know the exact cause of either problem. However, they have discovered that mutations in the gene that produces the SOD1 enzyme were associated with some cases of familial ALS. Scientists also theorize that multiple sclerosis may be caused by infection or vitamin D deficiency. ALS occurs between 50-70 years of age (the average age of occurrence ALS is 55), and mostly affects men. While MS occurs between 20-60 years of age, and mostly affects women. About 30,000 people in the US have ALS, and an average of 5,000 new diagnoses per year (that's about 15 new cases per week). Worldwide, MS affects more than 2.3 million people, with about 10,000 new cases diagnosed each year (that's about 200 new diagnoses per week).Some of the signs and symptoms of both diseases include muscle weakness, muscle spasms, problems walking, fatigue, slurred speech, and problems swallowing. ALS signs and symptoms that are different from MS include problems holding the head upright, clumsiness, muscle cramps and twitches, problems holding objects, and uncontrollable periods of laughing or crying. MS signs and symptoms that are different from ALS include vision problems, vertigo and balance problems, sexual problems, memory problems, depression, mood swings, and digestive problems. There is no cure for either disease, however the prognosis and life expectancy are different. Multiple sclerosis is not a fatal condition, while ALS progresses rapidly and leads to death.
Spinal Cord Injury
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Multiple Sclerosis (MS) Symptoms and Treatments
Multiple sclerosis (MS) symptoms vary from person to person, and can last for days to months without periods of remission. Symptoms of MS include sexual problems and problems with the bowel, bladder, eyes, muscles, speech, swallowing, brain, and nervous system. The early symptoms and signs of multiple sclerosis usually start between age 20 and 40. MS in children, teens, and those over age 40 is rare. Treatment options for multiple sclerosis vary depending on the type and severity of symptoms. Medications may be prescribed to manage MS symptoms.
Multiple Sclerosis (MS) Early Warning Signs and Types
Multiple sclerosis (MS) can be thought of as an immune-mediated inflammatory process involving different areas of the central nervous system (CNS) at various points in time. Early warning signs and symptoms of MS in children, teens, and adults are similar; however, children and teens with pediatric also may have seizures and a complete lack of energy. Adults with MS do not have these signs and symptoms. Other signs and symptoms of MS include inflammation of the optic nerve (optic neuritis), changes in vision, Wiping or having tissues around the eye and moving the eye may be painful, and double vision. There are four types of MS, relapsing remitting MS (RRMS), secondary progressive MS (SPMS), primary progressive MS (PPMS), and progressive relapsing MD (PRMS).
Is MS Contagious? (Multiple Sclerosis)
Multiple sclerosis, or MS, is a degenerative disease of the covering around the nerves in the central nervous system (CNS). Researchers and doctors don't know the exact cause, but many theorize that it may be due to environmental triggers, an autoimmune disease, and viruses (infections). Symptoms of MS include vision changes, paralysis, vertigo, heat intolerance, slurred speech, sexual dysfunction, and urinary incontinence (the inability to urinate). There's no vaccine or cure for MS, but the progression and symptoms of the disease can be treated.
Multiple Sclerosis (MS) and Pregnancy
Multiple sclerosis or MS is a central nervous system disease in which the immune system attacks the myelin sheath (the protective coating around nerves). Symptoms of MS include pain, sexual problems, fatigue, numbness and tingling, emotional changes, and depression.Women who are pregnant and have multiple sclerosis may have more difficulty carrying a pregnancy. Multiple sclerosis does not affect ability to conceive, and does not seem to affect fertility. MS symptoms during pregnancy may stay the same or get better; however, they may worsen after giving birth. Pregnancy decreases the number of relapses, but flares increase in the first 3-6 months after delivery. Pregnant women with MS may carrying a pregnancy more difficult to tell when labor starts, and there is an increased need to use forceps or vacuum to assist with delivery or b7 C-section (Cesarean birth) increases. Some treatment MS drugs may be safe to use during pregnancy; however, some drugs should not be taken, for example, baclofen (Gablofen, Lioresal), fluoxetine (Prozac, Sarafem), or solifenacin succinate (VESIcare), and most disease-modifying therapies (DMTs). Talk with your healthcare team about vitamins, supplements, and medications that you are taking if you are pregnant and have MS.
Alternative Treatment for MS (CAM for MS)
The term alternative therapy, in general, is used to describe any medical treatment or intervention that has not been scientifically documented or identified as safe or effective for a specific condition. Alternative therapy encompasses a variety of disciplines that range from diet and exercise to mental conditioning to lifestyle changes.
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Medications & Supplements
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.