Zanaflex

Primary Uses

Zanaflex is used to treat spasticity, a condition where muscles become stiff, tight, or spasm involuntarily. It works by temporarily relaxing muscle tone to help improve movement and comfort for individuals with certain neurological conditions.

Conditions Treated

This medication is typically prescribed for people with medical issues that affect the central nervous system, including:

• Multiple sclerosis (MS): A disease that affects the brain and spinal cord, often causing muscle tightness and spasms.
• Spinal cord injury: Damage to the spine that can lead to permanent or temporary muscle stiffness.

Because the effects of Zanaflex are short-lived, it is often used during specific times of the day when relief from muscle spasms is most important. This may include times when a person needs to perform daily activities or when they need to reduce discomfort to rest.

Mechanism of Action

Zanaflex belongs to a class of medications called central alpha-2-adrenergic agonists. It works by acting on the central nervous system, primarily within the spinal cord, to reduce muscle spasticity.

The medication functions by:

• Increasing inhibition: It increases presynaptic inhibition of motor neurons, which helps prevent overactive nerve signals.
• Reducing excitatory signals: It decreases the release of certain chemicals in the brain and spinal cord that normally tell muscles to contract.
• Slowing nerve impulses: By interfering with the transmission of nerve impulses, it helps calm the over-stimulated nerves that cause muscles to tighten or cramp.

The overall effect of Zanaflex is to temporarily relax muscle tone. This helps manage symptoms like muscle stiffness and spasms associated with conditions such as multiple sclerosis or spinal cord injuries. Because it is short-acting, the effects are most noticeable for a brief period after a dose is taken.

Common Side Effects

Some people taking Zanaflex may experience mild side effects. These commonly include:

• Drowsiness or sleepiness
• Dizziness
• Dry mouth
• Weakness or fatigue
• Constipation
• Vomiting
• Tingling sensations in the skin

Serious Side Effects

Contact a doctor immediately or seek emergency medical attention if you experience any of the following:

• Hallucinations or seeing things that are not there
• Severe confusion or nervousness
• Slow or irregular heartbeat
• Fainting or extreme lightheadedness
• Blurred vision
• Signs of liver injury, such as yellowing of the skin or eyes, dark urine, or pain in the upper right side of the stomach
• Unusual tiredness or loss of appetite

Stopping Zanaflex abruptly can lead to withdrawal symptoms, such as high blood pressure, a rapid heart rate, or tremors. Consult your doctor before making any changes to how you take this medication.

Hypotension and Fainting

Tizanidine can cause a significant drop in blood pressure, which may lead to dizziness, lightheadedness, or fainting. This risk is highest when starting the medication or when the dose is increased. To reduce the risk, changes in position, such as standing up from a sitting or lying position, should be done slowly.

Liver Health

There is a risk of liver injury associated with this medication. Healthcare providers typically monitor liver function through blood tests before starting treatment and periodically during the first few months of use. Symptoms of liver problems may include nausea, fatigue, loss of appetite, or yellowing of the skin or eyes.

Sedation and Alertness

Zanaflex often causes drowsiness and sedation. This effect can be increased when taken with alcohol or other medications that cause sleepiness. Activities requiring mental alertness, such as driving or operating machinery, should be approached with caution until the effects of the drug are known.

Drug Interactions

This medication is contraindicated for use with potent CYP1A2 inhibitors, such as fluvoxamine and ciprofloxacin. Combining these drugs can lead to dangerously high levels of tizanidine in the blood, increasing the risk of severe side effects.

Withdrawal Symptoms

Stopping Zanaflex suddenly, especially after long-term use or high doses, may cause withdrawal symptoms. These can include high blood pressure, a rapid heart rate, and increased muscle tension. Healthcare providers usually recommend tapering the dose gradually to avoid these effects.

Hallucinations

Some individuals may experience hallucinations or psychotic-like symptoms while taking this medication. If these occur, medical consultation is necessary.

Pregnancy

It is not known whether Zanaflex will harm an unborn baby. Animal studies have shown that high doses of the medication may lead to developmental issues and lower birth weights, though these effects often occurred at doses that were also toxic to the mother. Because there are no adequate, well-controlled studies in humans, healthcare providers typically only prescribe this medication during pregnancy if the potential benefit justifies the potential risk to the fetus.

Breastfeeding

It is currently unknown if Zanaflex passes into human breast milk. Research in animals has indicated that the drug is excreted in the milk of lactating rats. Because many drugs can pass into breast milk, caution is advised. If you are breastfeeding or planning to breastfeed, you should discuss the potential risks and benefits with your healthcare provider to determine the safest course of action.

If you are pregnant, planning to become pregnant, or nursing, it is important to consult with a clinician before starting or continuing this medication.

Available Forms

Zanaflex is available in the following oral forms:

• Tablets
• Capsules

The tablets and capsules are not bioequivalent, meaning the body absorbs them differently. Because of these differences, one form should not be substituted for the other without medical supervision. Additionally, the way food affects the absorption of these forms varies, so it is important to be consistent in how the medication is taken relative to meals.

FDA Approval and Indications

Zanaflex (tizanidine) is approved by the U.S. Food and Drug Administration (FDA) for the management of spasticity. Because the medication has a short duration of effect, the FDA-approved labeling suggests that treatment should be reserved for those daily activities and times when relief from spasticity is most important.

Generic Availability

Generic versions of tizanidine hydrochloride are FDA-approved and available in both tablet and capsule forms. Generic medications are required to meet the same quality, strength, and safety standards as the original brand-name drug.

Regulatory Warnings and Interactions

The FDA has updated regulatory labeling for Zanaflex to include contraindications regarding drug interactions. Specifically, Zanaflex must not be used with potent CYP1A2 inhibitors, such as fluvoxamine or ciprofloxacin. These interactions can cause a significant increase in tizanidine levels in the blood, potentially leading to severe adverse effects like low blood pressure or excessive sedation.

Risk of Withdrawal

Stopping Zanaflex abruptly, especially after long-term use or high daily doses, can lead to withdrawal symptoms. These symptoms often occur because the body has become accustomed to the medication's effects on the central nervous system.

Potential Symptoms

Withdrawal symptoms may include:

• High blood pressure (hypertension)
• Fast heart rate (tachycardia)
• Increased muscle tightness or spasms
• Tremors
• Anxiety

Safe Discontinuation

To minimize the risk of withdrawal, healthcare providers typically recommend tapering the medication. This involves slowly decreasing the dose over a period of time. You should not change your dose or stop taking Zanaflex without medical supervision.