What is Norflex? A Comprehensive Guide to the Muscle Relaxant

October 7, 2025 •

4 min read

Despite its brand name, Norflex, being discontinued in the U.S., the active ingredient, orphenadrine, is still used to treat muscle pain and stiffness. It is a centrally acting muscle relaxant that works by calming overactive nerves to help muscles relax.

Quick Summary

Norflex, orphenadrine, is a muscle relaxant prescribed as an adjunct to other therapies for acute musculoskeletal conditions like pain and stiffness. Its mechanism involves central nervous system depression and anticholinergic effects. Caution is advised due to potential side effects, interactions, and contraindications.

Key Points

Orphenadrine vs. Norflex: Norflex is the discontinued brand name for the generic muscle relaxant medication, orphenadrine.
Primary Use: It is prescribed as an adjunct to rest and physical therapy for the relief of pain associated with acute, painful musculoskeletal conditions.
Mechanism of Action: While not fully understood, it involves CNS depression and anticholinergic effects that help relax muscles and alleviate spasms.
Key Side Effects: Common side effects include drowsiness, dizziness, dry mouth, and blurred vision, which require medical guidance for management.
Important Contraindications: The medication should not be used by individuals with glaucoma, myasthenia gravis, or certain obstructive conditions affecting the bladder or intestines.
Drug Interactions: Orphenadrine can cause dangerous additive effects when combined with alcohol, other CNS depressants, or other anticholinergic drugs.
Adjunctive Therapy: Orphenadrine is not a primary treatment but rather a component of a larger treatment plan that should also include rest and physical therapy.

What is Norflex (Orphenadrine)?

Norflex is the former brand name for the generic drug orphenadrine, a prescription medication used to alleviate the pain and discomfort associated with acute musculoskeletal conditions. It is not a narcotic, but a skeletal muscle relaxant often used in conjunction with other treatments, such as physical therapy and rest, for strains, sprains, and other injuries. While the brand name Norflex is no longer marketed in the United States, the generic version, orphenadrine, is still available.

How does Norflex work?

The exact mechanism of action for orphenadrine is not fully understood, but its effects are primarily central rather than directly on the skeletal muscles themselves. It is believed to work through a combination of actions within the central nervous system (CNS):

CNS Depression: Orphenadrine is thought to act on motor centers in the brain to depress the CNS, which helps inhibit nerve impulses that lead to muscle spasms.
Anticholinergic Action: The medication also possesses anticholinergic properties, meaning it blocks the action of acetylcholine, a neurotransmitter. These effects can help with muscle relaxation but are also responsible for some of the common side effects, such as dry mouth and blurred vision.
Analgesic Properties: Some of orphenadrine's effectiveness may also be due to its mild pain-relieving (analgesic) effects.

Medical Uses and Administration

Orphenadrine is indicated for the short-term relief of discomfort from acute, painful musculoskeletal conditions. It is not a cure but an adjunctive therapy intended to relieve symptoms while the underlying condition is addressed through other means. In addition to muscle spasms, one form of orphenadrine has also been used to treat the trembling associated with Parkinson's disease.

Dosage and forms

Orphenadrine is available in several forms, and the appropriate dosage is determined by a healthcare professional based on the specific product and individual needs.

Extended-Release Tablets: This form is typically taken orally. These tablets should generally be swallowed whole and not crushed or chewed, unless directed by a healthcare provider.
Injection: For acute relief in a hospital or clinical setting, a healthcare provider may administer the medication via injection. Oral therapy is often used for maintenance as soon as appropriate.

Side Effects and Precautions

As with all medications, orphenadrine carries a risk of side effects, which are often related to its anticholinergic activity and can be more pronounced at higher doses.

Common side effects

Drowsiness and dizziness
Dry mouth
Nausea and vomiting
Constipation
Blurred vision
Headache
Urinary retention

Serious side effects

Fast or irregular heartbeat (tachycardia)
Confusion, anxiety, agitation, and hallucinations
Fainting or lightheadedness
Painful or difficult urination

Contraindications and precautions

Certain individuals should not take orphenadrine due to the risk of serious complications. It is contraindicated in patients with:

Glaucoma
Myasthenia gravis
Pyloric or duodenal obstruction
Stenosing peptic ulcer
Enlarged prostate or bladder neck obstruction
Cardio-spasm (megaesophagus)

Additionally, orphenadrine should be used with caution in elderly patients and those with heart conditions, as they are at increased risk for adverse effects.

Drug Interactions

Orphenadrine can interact with other medications, potentially increasing the risk of sedation and anticholinergic effects. It is crucial to inform your doctor about all medications, supplements, and herbal products you are taking. Major interactions include:

Central Nervous System (CNS) Depressants: Combining orphenadrine with alcohol, sleeping pills, other muscle relaxants, anxiety medication, or opioids can increase drowsiness and slow breathing, which can be dangerous or fatal.
Anticholinergic Agents: Using orphenadrine with other drugs that have anticholinergic properties can amplify side effects like dry mouth, constipation, and confusion.
Certain Heart Medications: Orphenadrine can interact with drugs like dofetilide and should be avoided or used with caution.

Comparison of Muscle Relaxants


Feature	Norflex (orphenadrine)	Flexeril (cyclobenzaprine)	Robaxin (methocarbamol)
Mechanism	Not fully understood; involves CNS depression and anticholinergic action	Acts in the brain to relieve muscle spasms	Depresses the central nervous system to relax muscles
Administration (Oral)	Extended-release tablets available	Immediate-release and extended-release tablets available	Tablets available
Primary Use	Acute painful musculoskeletal conditions, with some use for Parkinson's tremors	Short-term relief of acute muscle spasms	Relief of skeletal muscle spasms
Side Effects	Dry mouth, dizziness, drowsiness, constipation, blurred vision	Drowsiness, dry mouth, dizziness	Drowsiness, dizziness
Contraindications	Glaucoma, myasthenia gravis, heart problems, obstructive conditions	Severe liver problems	None listed with similar severity
Abuse Potential	Some reports of potential for misuse due to euphoric effects	Less potential for abuse compared to some others	Lower risk of addiction

Conclusion

Orphenadrine, known by the former brand name Norflex, is an effective muscle relaxant for the short-term treatment of acute musculoskeletal pain and stiffness. It works by acting on the central nervous system and possessing anticholinergic properties, helping to calm overactive nerves and relax muscles. However, its use is accompanied by a list of potential side effects, precautions, and drug interactions that must be carefully managed. As with any prescription medication, it is essential to use orphenadrine only under the supervision of a healthcare provider and to follow all instructions precisely to ensure safety and effectiveness.

For more detailed information, consult the manufacturer's FDA-approved prescribing information at accessdata.fda.gov.

Frequently Asked Questions

Yes, Norflex was the brand name for the generic drug orphenadrine. While the brand-name product has been discontinued in the United States, the generic version is still available by prescription.

Extended-release tablets should generally be swallowed whole with a full glass of water. Do not crush or chew the tablets unless directed by a healthcare provider, as this can affect how the medication is absorbed.

You should avoid drinking alcohol and using other CNS depressants, such as other muscle relaxants, sleeping pills, or opioid pain medication, as these can increase drowsiness and other side effects. Additionally, do not drive or operate heavy machinery until you know how the medication affects you.

No, Norflex is intended for short-term use as an adjunct to other therapies for acute, painful musculoskeletal conditions. The safety of long-term therapy has not been established, and ongoing medical evaluation is necessary for prolonged use.

Orphenadrine is contraindicated in patients with conditions including glaucoma, myasthenia gravis, obstructive stomach or intestinal issues, an enlarged prostate, or a hypersensitivity to the drug.

Clinical reviews suggest that orphenadrine can be effective for relieving non-specific lower back pain, but it should be used in conjunction with other treatments like rest and physical therapy. It is not a standalone treatment.

Use of orphenadrine in older adults should be done with caution, as they are more susceptible to anticholinergic side effects like confusion, sedation, and urinary retention. A healthcare provider will determine the appropriate approach for older patients.

If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and resume your regular schedule. Do not take a double dose to compensate for a missed one.