Zanaflex 2mg 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 muscle relaxant used to treat muscle spasms and stiffness (spasticity) caused by conditions like multiple sclerosis or spinal cord injury. It works by calming overactive nerves in the brain and spinal cord that control muscle movement.
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 local drug take-back programs.
Missing a Dose
If you take this medication regularly, take a 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 local drug take-back programs.
Missing a Dose
If you take this medication regularly, take a 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 driving or operating heavy machinery until you know how this medication affects you, as it can cause drowsiness and dizziness.
- Avoid alcohol consumption, as it can increase drowsiness and dizziness.
- Avoid abrupt discontinuation of the medication, as it can lead to withdrawal symptoms like increased spasticity, high blood pressure, and rapid heart rate. Doses should be tapered gradually.
- Take consistently with or without food to minimize variability in absorption and effects.
- Rise slowly from a sitting or lying position to minimize dizziness or fainting due to low blood pressure.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
Initial: 2 mg orally once daily. Titrate gradually. Maintenance: 2 mg to 4 mg orally three times daily.
Dose Range:
2 - 36 mg
Condition-Specific Dosing:
spasticity:
Initial 2 mg, increased by 2 mg to 4 mg at 1 to 4 day intervals. Max single dose 16 mg. Max daily dose 36 mg.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment for mild impairment, but caution advised.
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 poorly dialyzable. Use with caution, reduce dose, and monitor closely.
Hepatic Impairment:
Mild:
Caution advised, monitor LFTs.
Moderate:
Caution advised, monitor LFTs. Reduced clearance expected.
Severe:
Contraindicated in severe hepatic impairment. Caution advised, monitor LFTs. Reduced clearance expected.
Pharmacology
Mechanism of Action
Tizanidine is an alpha-2 adrenergic agonist. It reduces spasticity by increasing presynaptic inhibition of motor neurons at the spinal cord level, leading to a reduction in the release of excitatory amino acids. This results in decreased facilitation of spinal motor neurons.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 40% (capsule) to 68% (tablet) due to first-pass metabolism.
Tmax:
1 to 2 hours
FoodEffect:
Food increases Cmax and AUC for capsules, but decreases Cmax and increases AUC for tablets. Administration with food can reduce the risk of orthostatic hypotension. Consistent administration with or without food is recommended.
Distribution:
Vd:
Approximately 2.4 L/kg
ProteinBinding:
Approximately 30%
CnssPenetration:
Yes
Elimination:
HalfLife:
Approximately 2.5 hours (range 1.5-4 hours)
Clearance:
Approximately 2.4 L/hr/kg
ExcretionRoute:
Renal (approximately 60% of dose), Fecal (approximately 20%)
Unchanged:
Approximately 5% (renal)
Pharmacodynamics
OnsetOfAction:
Within 1 hour
PeakEffect:
1 to 2 hours
DurationOfAction:
3 to 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 lightheadedness, especially when standing up
- Fainting
- Signs of liver problems (e.g., unusual tiredness, nausea, vomiting, dark urine, yellowing of skin or eyes, stomach pain)
- Hallucinations (seeing or hearing things that are not there)
- Unusual muscle weakness or fatigue
- Slow heart rate
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, 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 your other medications and health conditions.
Remember, do not start, stop, or modify the dosage of any medication without first consulting your doctor. This will help prevent potential interactions and ensure your safety while taking this medication.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, 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 your other medications and health conditions.
Remember, do not start, stop, or modify the dosage of any medication without first consulting your doctor. This will help prevent potential interactions and ensure your safety while taking this medication.
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 discussing it with 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, plan to become pregnant, or are 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 discussing it with 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, plan to become pregnant, or are 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:
- Drowsiness
- Dizziness
- Lightheadedness
- Bradycardia (slow heart rate)
- Hypotension (low blood pressure)
- Respiratory depression (slow, shallow breathing)
- Coma
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Treatment is supportive, including gastric lavage, activated charcoal, and maintaining vital signs.
Drug Interactions
Contraindicated Interactions
- Fluvoxamine
- Ciprofloxacin
Major Interactions
- Other strong CYP1A2 inhibitors (e.g., Acyclovir, Amiodarone, Mexiletine, Propafenone, Verapamil, Zileuton, Cimetidine, Enoxacin, Pefloxacin, Norfloxacin, Rofecoxib, Ticlopidine)
- Other CNS depressants (e.g., alcohol, benzodiazepines, opioids, tricyclic antidepressants, sedating antihistamines)
- Antihypertensives (e.g., alpha-blockers, ACE inhibitors, diuretics, beta-blockers, calcium channel blockers)
Moderate Interactions
- Oral contraceptives (may increase tizanidine levels)
- Baclofen (additive CNS depression)
- Skeletal muscle relaxants (additive CNS depression)
- QT-prolonging drugs (theoretical risk, monitor ECG)
Minor Interactions
- Not available
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 initiation of therapy.
Blood Pressure (sitting and standing)
Rationale: To establish baseline and assess for orthostatic hypotension risk.
Timing: Prior to initiation of therapy.
Routine Monitoring
Liver Function Tests (ALT, AST)
Frequency: At 1, 3, and 6 months after initiation of therapy, and periodically thereafter, or if symptoms of liver injury occur.
Target: Within normal limits
Action Threshold: Discontinue if ALT or AST are persistently greater than 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: Within patient's normal range, without significant orthostatic drop.
Action Threshold: Significant symptomatic hypotension or orthostatic hypotension.
Renal Function (CrCl)
Frequency: Periodically, especially in patients with known or suspected renal impairment.
Target: Not applicable
Action Threshold: CrCl < 25 mL/min requires dose adjustment.
Symptom Monitoring
- Drowsiness
- Dizziness
- Dry mouth
- Asthenia (weakness)
- Hypotension (lightheadedness, fainting)
- Bradycardia
- Hallucinations
- Symptoms of liver injury (e.g., nausea, vomiting, dark urine, jaundice, abdominal pain, fatigue)
- Withdrawal symptoms (e.g., rebound spasticity, tachycardia, hypertension, hypertonia, anxiety, tremor) if abruptly discontinued
Special Patient Groups
Pregnancy
Category C. Use only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects.
Trimester-Specific Risks:
First Trimester:
Potential for developmental toxicity based on animal data.
Second Trimester:
Potential for developmental toxicity based on animal data.
Third Trimester:
Potential for developmental toxicity based on animal data; risk of neonatal withdrawal is unknown.
Lactation
Tizanidine is excreted in human milk. Due to the potential for serious adverse reactions in breastfed infants, 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 cannot be ruled out. Potential for sedation, hypotonia, and other CNS effects in the infant.
Pediatric Use
Safety and effectiveness have not been established in pediatric patients. Not recommended for use in this population.
Geriatric Use
Use with caution in elderly patients due to increased sensitivity to adverse effects (e.g., sedation, hypotension, dry mouth, asthenia). Start with lower doses and titrate slowly. Renal function should be monitored.
Clinical Information
Clinical Pearls
- Tizanidine capsules and tablets are not bioequivalent and cannot be interchanged on a milligram-for-milligram basis without re-titration.
- Food significantly affects the bioavailability of tizanidine, especially for capsules. Advise patients to take it consistently with or without food.
- Abrupt discontinuation can lead to rebound spasticity, tachycardia, and hypertension. Taper dose slowly over 2-4 weeks.
- Monitor liver function tests (LFTs) at baseline, 1, 3, and 6 months, and periodically thereafter, or if symptoms of liver injury occur.
- Be aware of significant drug interactions, especially with strong CYP1A2 inhibitors (e.g., fluvoxamine, ciprofloxacin) which are contraindicated.
- Warn patients about potential for hypotension, especially orthostatic hypotension, and CNS depression (drowsiness, dizziness).
- Consider lower starting doses and slower titration in patients with renal impairment or in the elderly.
Alternative Therapies
- Baclofen
- Diazepam
- Dantrolene
- Gabapentin
- Botulinum toxin (for focal spasticity)
Cost & Coverage
Average Cost:
Varies widely, typically $10-$50 per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (for generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure 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 medical attention. When seeking help, be prepared to provide details about the medication, including the amount taken and the time it happened, to ensure you receive the best possible care.