Orphenadrine Citrate 100mg ER Tabs
It is used to relax muscles.
Drug Class
Skeletal Muscle Relaxant
Pharmacologic Class
Anticholinergic Agent; Antihistamine (weak); NMDA Receptor Antagonist (weak)
Pregnancy Category
Category C
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Orphenadrine is a medication used to help relax muscles and relieve pain and stiffness caused by muscle injuries or conditions. It works by affecting the brain and nervous system, rather than directly on the muscles themselves. It's often used along with rest and physical therapy.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. You can take this medication with or without food. If it causes stomach upset, take it with food to help minimize this side effect. It's essential to swallow the medication whole and not chew, break, or crush it.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry location, avoiding bathrooms. Keep all medications in a safe place, 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. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs for a safe and environmentally friendly way to dispose of your medication.
Missing a Dose
If you take this medication regularly and miss a dose, take it 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, be sure not to take it more frequently than directed by your doctor.
To use this medication correctly, follow your doctor's instructions and read all the information provided. You can take this medication with or without food. If it causes stomach upset, take it with food to help minimize this side effect. It's essential to swallow the medication whole and not chew, break, or crush it.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry location, avoiding bathrooms. Keep all medications in a safe place, 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. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs for a safe and environmentally friendly way to dispose of your medication.
Missing a Dose
If you take this medication regularly and miss a dose, take it 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, be sure not to take it more frequently than directed by your doctor.
Lifestyle & Tips
- Avoid driving or operating heavy machinery until you know how this medication affects you, as it can cause dizziness or drowsiness.
- Avoid alcohol and other CNS depressants, as they can increase drowsiness and other side effects.
- To relieve dry mouth, suck on sugarless candy or ice chips, or use a saliva substitute.
- Increase fluid intake and fiber in your diet to help prevent constipation.
- Report any vision changes, difficulty urinating, or severe confusion to your doctor.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
100 mg twice daily (every 12 hours)
Dose Range:
100 - 200 mg
Condition-Specific Dosing:
acute painful musculoskeletal conditions:
100 mg twice daily
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 dose adjustment recommended, use with caution.
Moderate:
Use with caution, monitor for increased anticholinergic effects.
Severe:
Use with caution, monitor for increased anticholinergic effects; consider lower dose or extended interval.
Dialysis:
Not well studied; likely not dialyzable due to high protein binding and large volume of distribution. Use with extreme caution.
Hepatic Impairment:
Mild:
No specific dose adjustment recommended, use with caution.
Moderate:
Use with caution, monitor for increased anticholinergic effects; consider lower dose.
Severe:
Contraindicated in severe hepatic impairment due to extensive hepatic metabolism.
Confidence:
Medium
Pharmacology
Mechanism of Action
Orphenadrine is a centrally acting skeletal muscle relaxant. Its exact mechanism is not fully understood but is believed to be related to its analgesic and anticholinergic properties. It does not directly relax tense skeletal muscles in man. It may act by blocking central cholinergic receptors, thereby reducing muscle spasm associated with painful musculoskeletal conditions. It also possesses some antihistaminic and local anesthetic properties.
Pharmacokinetics
Absorption:
Bioavailability:
Well absorbed orally, but specific percentage not widely reported for ER formulation.
Tmax:
Approximately 6-8 hours for extended-release formulation.
FoodEffect:
Food may slightly delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
Large volume of distribution (approximately 100 L/kg), indicating extensive tissue distribution.
ProteinBinding:
Approximately 95%
CnssPenetration:
Yes (crosses the blood-brain barrier due to its central effects)
Elimination:
HalfLife:
Approximately 14-16 hours (for extended-release formulation); ranges from 13-20 hours.
Clearance:
Not readily available, but primarily hepatic.
ExcretionRoute:
Primarily renal (urine) as metabolites, with a small amount excreted unchanged. Some fecal excretion.
Unchanged:
Less than 8% (renal)
Pharmacodynamics
OnsetOfAction:
Within 1 hour (for immediate release, ER onset is slower)
PeakEffect:
Not precisely defined for muscle relaxation, but peak plasma levels are reached in 6-8 hours for ER.
DurationOfAction:
Approximately 12 hours (for extended-release formulation)
Confidence:
Medium
Safety & Warnings
Side Effects
Serious Side Effects: Seek Medical Attention Immediately
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
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
Severe dizziness or fainting
Confusion
Anxiety
Abnormal or rapid heartbeat
Changes in vision, eye pain, or severe eye irritation
Difficulty urinating
Hallucinations (seeing or hearing things that are not there)
Shakiness
Agitation
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Upset stomach or vomiting
Dry mouth
Dizziness, drowsiness, tiredness, or weakness
Headache
* Constipation
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. 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.
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
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
Severe dizziness or fainting
Confusion
Anxiety
Abnormal or rapid heartbeat
Changes in vision, eye pain, or severe eye irritation
Difficulty urinating
Hallucinations (seeing or hearing things that are not there)
Shakiness
Agitation
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Upset stomach or vomiting
Dry mouth
Dizziness, drowsiness, tiredness, or weakness
Headache
* Constipation
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. 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
- Blurred vision or eye pain
- Difficulty urinating
- Severe constipation
- Confusion or hallucinations
- Fast or irregular heartbeat
- Allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing)
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 symptoms you experienced.
Certain health conditions, including:
+ Enlarged prostate gland
+ Glaucoma
+ Bowel blockage
+ Myasthenia gravis
+ Ulcer disease
+ Difficulty urinating
+ Swallowing problems
Please note that this list is not exhaustive, and it is crucial to discuss all your health problems with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription and over-the-counter (OTC) drugs
Natural products
* Vitamins
This information will help your healthcare team determine whether it is safe for you to take this medication with your existing medications and health conditions. Never start, stop, or change the dose 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, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
Certain health conditions, including:
+ Enlarged prostate gland
+ Glaucoma
+ Bowel blockage
+ Myasthenia gravis
+ Ulcer disease
+ Difficulty urinating
+ Swallowing problems
Please note that this list is not exhaustive, and it is crucial to discuss all your health problems with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription and over-the-counter (OTC) drugs
Natural products
* Vitamins
This information will help your healthcare team determine whether it is safe for you to take this medication with your existing medications and health conditions. Never start, stop, or change the dose 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. Until you understand how this drug affects you, avoid operating a vehicle or engaging in activities that require alertness. If you are taking this medication long-term, your doctor may recommend regular blood tests to monitor your condition.
Before consuming alcohol, using marijuana or other cannabis products, or taking prescription or over-the-counter medications that can cause drowsiness, consult with your doctor. This medication is typically used in conjunction with rest, physical therapy, pain management medications, and other therapies to achieve optimal results.
If you are 65 years or older, exercise caution when using this medication, as you may be more susceptible to side effects. Pregnant women, those planning to become pregnant, or breastfeeding mothers should discuss the potential benefits and risks of this medication with their doctor to make an informed decision.
Before consuming alcohol, using marijuana or other cannabis products, or taking prescription or over-the-counter medications that can cause drowsiness, consult with your doctor. This medication is typically used in conjunction with rest, physical therapy, pain management medications, and other therapies to achieve optimal results.
If you are 65 years or older, exercise caution when using this medication, as you may be more susceptible to side effects. Pregnant women, those planning to become pregnant, or breastfeeding mothers should discuss the potential benefits and risks of this medication with their doctor to make an informed decision.
Overdose Information
Overdose Symptoms:
- Severe anticholinergic effects (e.g., dilated pupils, hot/dry skin, absent bowel sounds, urinary retention)
- CNS depression (e.g., profound drowsiness, coma)
- CNS excitation (e.g., agitation, hallucinations, seizures)
- Tachycardia
- Arrhythmias
- Respiratory depression
- Hypotension
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Treatment is supportive and symptomatic, including gastric lavage, activated charcoal, and physostigmine for severe anticholinergic symptoms (with caution).
Drug Interactions
Contraindicated Interactions
- Propoxyphene (due to increased risk of CNS toxicity, including confusion, anxiety, and tremors)
Major Interactions
Moderate Interactions
- Monoamine Oxidase Inhibitors (MAOIs) - theoretical risk of increased anticholinergic effects or hypertensive crisis (though less common than with TCAs)
- Drugs that prolong QT interval - theoretical risk due to anticholinergic effects (rarely reported)
Minor Interactions
- Not specifically identified as minor, but general caution with drugs affecting gastric motility due to anticholinergic effects.
Monitoring
Baseline Monitoring
Patient history (glaucoma, prostatic hypertrophy, myasthenia gravis, urinary retention, cardiac conditions)
Rationale: To identify contraindications or conditions requiring caution due to anticholinergic effects.
Timing: Prior to initiation of therapy
Baseline vital signs (heart rate, blood pressure)
Rationale: To establish baseline and monitor for potential cardiovascular effects (e.g., tachycardia).
Timing: Prior to initiation of therapy
Routine Monitoring
Effectiveness of muscle spasm relief
Frequency: Regularly during therapy
Target: Reduction in pain and muscle stiffness
Action Threshold: Lack of efficacy may require re-evaluation of treatment plan.
Anticholinergic side effects (e.g., dry mouth, blurred vision, urinary retention, constipation)
Frequency: Regularly during therapy
Target: Absence or mild, tolerable symptoms
Action Threshold: Severe or intolerable symptoms may require dose reduction or discontinuation.
CNS side effects (e.g., dizziness, drowsiness, confusion)
Frequency: Regularly during therapy
Target: Absence or mild, tolerable symptoms
Action Threshold: Severe or intolerable symptoms, especially in elderly, may require dose reduction or discontinuation.
Symptom Monitoring
- Dry mouth
- Blurred vision
- Urinary retention
- Constipation
- Dizziness
- Drowsiness
- Confusion (especially in elderly)
- Nausea
- Vomiting
- Headache
- Palpitations
- Tachycardia
Special Patient Groups
Pregnancy
Use only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects, but there are no adequate and well-controlled studies in pregnant women.
Trimester-Specific Risks:
First Trimester:
Potential for teratogenicity, though human data are limited.
Second Trimester:
Limited data, potential for anticholinergic effects on fetus.
Third Trimester:
Potential for anticholinergic effects on fetus and neonate (e.g., urinary retention, decreased GI motility).
Lactation
It is not known whether orphenadrine is excreted in human milk. Due to potential for serious adverse reactions in nursing infants (e.g., sedation, anticholinergic effects), 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 level L3 (Moderately Safe) - potential for sedation, irritability, or anticholinergic effects in infant. Monitor infant for drowsiness, feeding difficulties, or unusual behavior.
Pediatric Use
Safety and effectiveness have not been established in pediatric patients. Not recommended for use in children.
Geriatric Use
Use with caution in elderly patients due to increased susceptibility to anticholinergic side effects (e.g., confusion, hallucinations, urinary retention, constipation) and CNS depression. Start with lower doses and titrate slowly. Avoid in elderly with cognitive impairment or high anticholinergic burden.
Clinical Information
Clinical Pearls
- Orphenadrine is often used as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute painful musculoskeletal conditions.
- Due to its anticholinergic properties, it should be used with extreme caution or avoided in patients with glaucoma, myasthenia gravis, prostatic hypertrophy, or urinary retention.
- The extended-release formulation helps maintain consistent drug levels and allows for twice-daily dosing, improving patient adherence.
- Patients should be advised about the potential for additive CNS depression when combined with alcohol or other sedatives.
- The combination with propoxyphene is contraindicated due to severe CNS toxicity.
Alternative Therapies
- Cyclobenzaprine (Flexeril)
- Tizanidine (Zanaflex)
- Baclofen (Lioresal)
- Methocarbamol (Robaxin)
- Carisoprodol (Soma)
- Metaxalone (Skelaxin)
- Non-steroidal anti-inflammatory drugs (NSAIDs)
- Acetaminophen
Cost & Coverage
Average Cost:
Typically $15 - $50 per 30 tablets (generic)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 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. If you have any questions or concerns about this medication, don't hesitate to discuss them with 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 reporting the incident, be prepared to provide details about the medication taken, the amount, and the time it occurred.