Zanaflex 4mg Capsules
It is used to relax muscles.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Skeletal muscle relaxant
Pharmacologic Class
Alpha-2 adrenergic agonist
Pregnancy Category
Category C
FDA Approved
Dec 1996
DEA Schedule
Not Controlled
Overview
What is this medicine?
Tizanidine is a medication used to relax muscles and relieve muscle spasms caused by conditions like multiple sclerosis or spinal cord injury. It works by acting on the nervous system to reduce muscle stiffness and tightness.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. You can take this medication with or without food, but it's essential to take it the same way each time. Choose to take it either always with food or always on an empty stomach to maintain consistency.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless instructed to do so by your pharmacist. Instead, check with your pharmacist for guidance on the best disposal method or explore drug take-back programs in your area.
What to Do If You Miss a Dose
If you take this medication regularly, take the missed dose as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, follow your doctor's instructions and do not take it more frequently than recommended.
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. You can take this medication with or without food, but it's essential to take it the same way each time. Choose to take it either always with food or always on an empty stomach to maintain consistency.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless instructed to do so by your pharmacist. Instead, check with your pharmacist for guidance on the best disposal method or explore drug take-back programs in your area.
What to Do If You Miss a Dose
If you take this medication regularly, take the missed dose as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, follow your doctor's instructions and do not take it more frequently than recommended.
Lifestyle & Tips
- Avoid alcohol and other CNS depressants (e.g., sedatives, tranquilizers) as they can increase drowsiness and dizziness.
- Do not drive or operate heavy machinery until you know how this medication affects you, as it can cause drowsiness and dizziness.
- Take this medication consistently with or without food, but always the same way (e.g., always with food, or always without food) to ensure consistent absorption.
- Do not stop taking this medication suddenly, especially if you have been on it for a long time or at high doses. Abrupt discontinuation can lead to rebound hypertension, tachycardia, and increased spasticity. Your doctor will guide you on how to slowly reduce the dose.
- Report any signs of liver problems (e.g., unusual tiredness, nausea, vomiting, dark urine, yellowing of skin/eyes, abdominal pain) to your doctor immediately.
- Be aware of potential for low blood pressure (dizziness, lightheadedness, especially when standing up quickly).
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
Initial dose 2 mg orally once daily, titrated gradually.
Dose Range:
2 - 36 mg
Condition-Specific Dosing:
spasticity:
Initial 2 mg, increased by 2-4 mg increments every 1-4 days. Usual therapeutic range 8-36 mg/day in 3-4 divided doses. Max single dose 16 mg. Max daily dose 36 mg.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established (Safety and efficacy not established in pediatric patients)
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment for CrCl > 25 mL/min, but monitor for adverse effects.
Moderate:
For CrCl < 25 mL/min, reduce initial dose by 50% (e.g., 2 mg once daily) and titrate slowly. Monitor for adverse effects.
Severe:
For CrCl < 25 mL/min, reduce initial dose by 50% (e.g., 2 mg once daily) and titrate slowly. Monitor for adverse effects.
Dialysis:
Tizanidine is not significantly removed by hemodialysis. Dose adjustment needed as per severe renal impairment.
Hepatic Impairment:
Mild:
Use with caution. Monitor LFTs and for adverse effects.
Moderate:
Use with caution. Monitor LFTs and for adverse effects. Consider lower starting dose and slower titration.
Severe:
Contraindicated in patients with significant hepatic impairment (e.g., cirrhosis) due to increased exposure and risk of adverse effects.
Pharmacology
Mechanism of Action
Tizanidine is an alpha-2 adrenergic agonist. It reduces spasticity by increasing presynaptic inhibition of motor neurons at the alpha-2 adrenergic receptors, primarily within the spinal cord. This leads to a reduction in the release of excitatory amino acids, thereby decreasing muscle tone and reflex activity.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 40%
Tmax:
1-2 hours (capsules)
FoodEffect:
Food significantly increases Cmax (by approximately 30%) and AUC (by approximately 20%) when taken with a high-fat meal, and delays Tmax. Administer consistently with or without food.
Distribution:
Vd:
Approximately 2.4 L/kg
ProteinBinding:
Approximately 30%
CnssPenetration:
Yes
Elimination:
HalfLife:
Approximately 2.5 hours
Clearance:
Approximately 2.4 L/hr/kg
ExcretionRoute:
Renal (approximately 60% of dose), Fecal (approximately 20% of dose)
Unchanged:
Approximately 5% (renal)
Pharmacodynamics
OnsetOfAction:
Within 1 hour
PeakEffect:
1-2 hours
DurationOfAction:
3-6 hours
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Signs of a urinary tract infection (UTI), such as:
+ Blood in the urine
+ Burning or pain when passing urine
+ Frequent or urgent need to urinate
+ Fever
+ Lower stomach pain
+ Pelvic pain
Severe dizziness or fainting
Confusion
Hallucinations (seeing or hearing things that are not there)
Mood changes
Changes in behavior
Slow heartbeat
Fever, chills, or sore throat
Other Possible Side Effects
Most people do not experience significant side effects, but some may occur. If you notice any of the following side effects or any other unusual symptoms, contact your doctor for advice:
Dry mouth
Dizziness
Drowsiness
Fatigue
* Weakness
Not all side effects are listed here. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of liver problems, including:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Signs of a urinary tract infection (UTI), such as:
+ Blood in the urine
+ Burning or pain when passing urine
+ Frequent or urgent need to urinate
+ Fever
+ Lower stomach pain
+ Pelvic pain
Severe dizziness or fainting
Confusion
Hallucinations (seeing or hearing things that are not there)
Mood changes
Changes in behavior
Slow heartbeat
Fever, chills, or sore throat
Other Possible Side Effects
Most people do not experience significant side effects, but some may occur. If you notice any of the following side effects or any other unusual symptoms, contact your doctor for advice:
Dry mouth
Dizziness
Drowsiness
Fatigue
* Weakness
Not all side effects are listed here. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe dizziness or fainting spells
- Yellowing of the skin or eyes (jaundice)
- Dark urine
- Persistent nausea or vomiting
- Unusual tiredness or weakness
- Severe abdominal pain
- Difficulty breathing or swallowing
- Rash or hives
- Swelling of the face, lips, tongue, or throat
- Sudden increase in blood pressure or heart rate after stopping the medication
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, any of its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you are currently taking ciprofloxacin or fluvoxamine, as these medications may interact with this drug.
Please note that this is not an exhaustive list of all potential interactions. To ensure your safety, it is crucial to disclose all of your medications, including:
Prescription and over-the-counter (OTC) drugs
Natural products
* Vitamins
Additionally, inform your doctor about any existing health problems. It is vital to verify that it is safe to take this medication in conjunction with all of your other medications and health conditions.
Remember, do not start, stop, or modify the dosage of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, any of its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you are currently taking ciprofloxacin or fluvoxamine, as these medications may interact with this drug.
Please note that this is not an exhaustive list of all potential interactions. To ensure your safety, it is crucial to disclose all of your medications, including:
Prescription and over-the-counter (OTC) drugs
Natural products
* Vitamins
Additionally, inform your doctor about any existing health problems. It is vital to verify that it is safe to take this medication in conjunction with all of your other medications and health conditions.
Remember, do not start, stop, or modify the dosage of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
To ensure your safety, avoid driving and other activities that require alertness until you understand how this medication affects you. When getting up from a sitting or lying down position, rise slowly to minimize the risk of dizziness or fainting. Be cautious when climbing stairs.
Before consuming alcohol, marijuana, or other forms of cannabis, or taking prescription or over-the-counter medications that may impair your reactions, consult with your doctor.
If you have been taking a high dose of this medication or using it regularly, do not stop taking it abruptly without first consulting your doctor. Stopping the medication suddenly may increase your risk of side effects. If you need to discontinue use, your doctor will guide you on how to gradually stop taking it.
As directed by your doctor, have your blood tested regularly and discuss the results with them.
Do not switch between the capsule and tablet forms of this medication without consulting your doctor. If your doctor changes your medication from one form to another (e.g., from capsules to tablets), the new form may interact differently with food. Your doctor may monitor you closely after switching to the new form to check for any differences in how it works or potential side effects.
Animal studies have shown that this medication can cause fertility problems. Although it is unclear if this medication affects human fertility, discuss any concerns with your doctor.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. You and your doctor will need to discuss the potential benefits and risks of this medication to you and your baby.
To ensure your safety, avoid driving and other activities that require alertness until you understand how this medication affects you. When getting up from a sitting or lying down position, rise slowly to minimize the risk of dizziness or fainting. Be cautious when climbing stairs.
Before consuming alcohol, marijuana, or other forms of cannabis, or taking prescription or over-the-counter medications that may impair your reactions, consult with your doctor.
If you have been taking a high dose of this medication or using it regularly, do not stop taking it abruptly without first consulting your doctor. Stopping the medication suddenly may increase your risk of side effects. If you need to discontinue use, your doctor will guide you on how to gradually stop taking it.
As directed by your doctor, have your blood tested regularly and discuss the results with them.
Do not switch between the capsule and tablet forms of this medication without consulting your doctor. If your doctor changes your medication from one form to another (e.g., from capsules to tablets), the new form may interact differently with food. Your doctor may monitor you closely after switching to the new form to check for any differences in how it works or potential side effects.
Animal studies have shown that this medication can cause fertility problems. Although it is unclear if this medication affects human fertility, discuss any concerns with your doctor.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. You and your doctor will need to discuss the potential benefits and risks of this medication to you and your baby.
Overdose Information
Overdose Symptoms:
- Hypotension (low blood pressure)
- Bradycardia (slow heart rate)
- Drowsiness
- Dizziness
- Somnolence
- Miosis (constricted pupils)
- Respiratory depression
- Coma
What to Do:
Seek immediate medical attention. Call 911 or your local emergency number. For poison control, call 1-800-222-1222. Treatment is supportive, including maintaining airway, breathing, and circulation, and managing hypotension with IV fluids and vasopressors if needed. Gastric lavage or activated charcoal may be considered if ingestion is recent.
Drug Interactions
Contraindicated Interactions
- Strong CYP1A2 inhibitors (e.g., fluvoxamine, ciprofloxacin)
- Moderate CYP1A2 inhibitors (e.g., zileuton, oral contraceptives, mexiletine, propafenone, verapamil, acyclovir, famotidine, ticagrelor)
Major Interactions
- Other CNS depressants (e.g., alcohol, benzodiazepines, opioids, tricyclic antidepressants, sedating antihistamines) - increased sedation and hypotension
- Antihypertensives (e.g., diuretics, ACE inhibitors, beta-blockers) - increased risk of hypotension and bradycardia
- Alpha-2 adrenergic agonists (e.g., clonidine) - additive hypotensive effects
- QT-prolonging drugs - theoretical risk of additive QT prolongation (monitor ECG)
Moderate Interactions
- CYP1A2 substrates (e.g., theophylline, caffeine) - potential for increased levels of substrate if tizanidine inhibits CYP1A2 (less likely as tizanidine is a substrate)
- Hepatotoxic drugs - increased risk of liver injury
Minor Interactions
- Not specifically identified as minor, but general caution with any drug affecting CNS or blood pressure.
Monitoring
Baseline Monitoring
Liver Function Tests (ALT, AST)
Rationale: To establish baseline and identify pre-existing hepatic impairment, as tizanidine can cause liver injury.
Timing: Prior to initiating therapy.
Blood Pressure (sitting and standing)
Rationale: To establish baseline and assess risk for hypotension, a common adverse effect.
Timing: Prior to initiating therapy.
Routine Monitoring
Liver Function Tests (ALT, AST)
Frequency: At 1, 3, and 6 months after initiation, and periodically thereafter, or if symptoms of liver injury occur.
Target: Within normal limits (WNL)
Action Threshold: Discontinue if ALT or AST are persistently >3 times the upper limit of normal (ULN) or if accompanied by clinical symptoms of liver injury.
Blood Pressure (sitting and standing)
Frequency: Periodically, especially during dose titration and if symptoms of hypotension occur.
Target: Maintain within patient's normal range, avoid symptomatic hypotension.
Action Threshold: If symptomatic hypotension or significant orthostatic changes occur, reduce dose or discontinue.
Heart Rate
Frequency: Periodically, especially during dose titration.
Target: WNL
Action Threshold: If significant bradycardia occurs, reduce dose or discontinue.
Sedation/Drowsiness
Frequency: Daily, especially during dose titration.
Target: Minimal impact on daily activities.
Action Threshold: If excessive, impairing daily function, reduce dose.
Efficacy (Spasticity reduction)
Frequency: Regularly during titration and maintenance.
Target: Improved muscle tone, reduced spasms, improved function.
Action Threshold: If inadequate response at maximum tolerated dose, consider alternative therapy.
Symptom Monitoring
- Dizziness
- Drowsiness/Sedation
- Dry mouth
- Hypotension (lightheadedness, fainting)
- Bradycardia
- Muscle weakness
- Signs of liver injury (e.g., nausea, vomiting, dark urine, jaundice, abdominal pain, fatigue)
- Rebound hypertension/tachycardia upon abrupt discontinuation
Special Patient Groups
Pregnancy
Category C. Animal studies have shown adverse effects on the fetus, but there are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus.
Trimester-Specific Risks:
First Trimester:
Potential for developmental toxicity observed in animal studies.
Second Trimester:
Potential for developmental toxicity observed in animal studies.
Third Trimester:
Potential for developmental toxicity observed in animal studies; risk of neonatal withdrawal symptoms is unknown but possible with alpha-2 agonists.
Lactation
It is not known whether tizanidine is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from tizanidine, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Infant Risk:
Risk unknown; potential for sedation, hypotension, and other adverse effects in the infant. Caution advised.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established. Not recommended for use in this population.
Geriatric Use
Use with caution in elderly patients due to increased sensitivity to adverse effects (e.g., hypotension, sedation, dry mouth, asthenia). Consider lower starting doses and slower titration. Renal function should be monitored.
Clinical Information
Clinical Pearls
- Tizanidine's efficacy is dose-dependent, but so are its side effects. Titrate slowly to find the optimal balance.
- Food significantly impacts tizanidine's absorption. Advise patients to take it consistently either always with food or always without food to minimize variability in drug levels and effects.
- Abrupt discontinuation can lead to rebound hypertension and tachycardia. Always taper the dose gradually.
- Monitor liver function tests at baseline, 1, 3, and 6 months, and periodically thereafter, or if symptoms of liver injury occur.
- Strong and moderate CYP1A2 inhibitors are contraindicated due to significant increases in tizanidine levels and risk of severe hypotension and sedation.
- Patients should be warned about the potential for significant drowsiness and dizziness, especially at the start of therapy or with dose increases, and advised against driving or operating machinery.
Alternative Therapies
- Baclofen (GABA-B agonist)
- Diazepam (Benzodiazepine)
- Dantrolene (Direct-acting muscle relaxant)
- Botulinum toxin injections (for focal spasticity)
- Gabapentin (Anticonvulsant with muscle relaxant properties)
- Pregabalin (Anticonvulsant with muscle relaxant properties)
Cost & Coverage
Average Cost:
$15 - $50 per 30 capsules (4mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.