Flexeril vs Norflex

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For patients experiencing muscle spasms or pain due to injuries, conditions like fibromyalgia, or other muscular related disorders, certain drugs that affect the signals sent to your brain from the nerves can help in alleviating discomfort and managing symptoms. Flexeril (cyclobenzaprine) and Norflex (orphenadrine) are two such medications often prescribed for these cases. Both belong to a class of drugs known as muscle relaxants but work slightly differently within the body. Flexeril acts centrally within the brain stem to produce its relaxing effects on skeletal muscles, primarily via noradrenergic neuron blocking. On the other hand, Norflex is classified as an anticholinergic drug that works by blocking certain nerve impulses causing pain sensations thus providing relief.

What is Flexeril?

Cyclobenzaprine (the generic name for Flexeril) was the first drug of its kind, a muscle relaxant that marked a significant development over previous antispasmodic medications. Cyclobenzaprine was first approved by the FDA in 1977. It works to relieve skeletal muscle spasms and associated pain without affecting overall muscle function, effectively "relaxing" muscles without causing undue weakness or impairments. It is prescribed for short-term relief from acute, painful musculoskeletal conditions.

On the other hand, Orphenadrine Citrate (the generic name for Norflex) also belongs to the class of drugs known as muscle relaxants and has been used to treat similar conditions since it received FDA approval in 1952. Like cyclobenzaprine, Norflex functions by blocking nerve impulses sent to the brain that cause pain sensations and muscular tension.

However, while both drugs are effective at relieving symptoms of musculoskeletal discomfort, their side effect profiles differ slightly due to their chemical structure differences. For example, Cyclobenzaprine's sedative effects are often more pronounced than those experienced with Orphenadrine Citrate.

What conditions is Flexeril approved to treat?

Flexeril is approved for the relief of muscle spasms associated with acute, painful musculoskeletal conditions:

  • Muscle spasm due to injury or other short-term musculoskeletal conditions
  • Fibromyalgia (off-label use)

Norflex, on the other hand, is also used in managing pain and discomfort caused by strains, sprains and other muscle injuries. It works primarily as a muscle relaxant in combination with rest and physical therapy.

How does Flexeril help with these illnesses?

Flexeril works to manage muscle spasms and associated pain by blocking nerve impulses (or pain sensations) that are sent to your brain. It does this by acting as a central nervous system depressant and skeletal muscle relaxant, thereby reducing motor activity of the muscles. Flexeril is primarily employed in the treatment of musculoskeletal conditions and spasticity from upper motor neuron syndromes.

Norflex operates in a similar way, but it also has anticholinergic properties inhibiting the transmission of parasympathetic nerve impulses, which can affect different parts of the body like heart rate or salivation. Both Flexeril and Norflex can provide relief from discomfort related to acute painful musculoskeletal conditions, their use should be combined with rest and physical therapy for optimal results.

What is Norflex?

Norflex, also known by its generic name Orphenadrine, is a muscle relaxant that works by blocking pain sensations and is often used to treat skeletal muscle conditions such as injury or spasms. It was first approved by the FDA in 1957. Unlike cyclobenzaprine (the active ingredient in Flexeril), Norflex does not primarily act on serotonin receptors; instead, it blocks acetylcholine at muscarinic acetylcholine receptors.

This difference means that Norflex has a somewhat different side-effect profile compared to SSRIs like Flexeril: specifically, it's less likely to cause drowsiness and dry mouth but may instead lead to blurred vision or urinary retention due to its anticholinergic effects. This makes it potentially more beneficial for some patients who do not respond well or have intolerable side effects with typical muscle relaxants like Flexeril.

What conditions is Norflex approved to treat?

Norflex is a prescription medication that has been approved by the FDA for use in treating:

  • Acute musculoskeletal pain due to muscle injury or strain
  • Pain related to certain types of muscular conditions, such as Parkinson's disease or multiple sclerosis.

How does Norflex help with these illnesses?

Norflex, also known as orphenadrine, is a muscle relaxant that works by blocking certain neurotransmitters in the central nervous system. It plays roles in many body functions such as muscle coordination and control, pain perception, and response to stress. Low levels of these neurotransmitters have been implicated in conditions like Parkinson's disease and muscle spasms. Norflex works by increasing their availability within the brain and spinal cord, thereby alleviating some symptoms associated with these conditions. Its action on histamine receptors may also play a role in its ability to relieve pain and inflammation related to musculoskeletal conditions. Since it does not significantly affect serotonin levels but targets other pathways instead, it is sometimes prescribed when a patient does not respond well to typical muscle relaxants (such as Flexeril), or may be combined with them for better effect.

How effective are both Flexeril and Norflex?

Both cyclobenzaprine (Flexeril) and orphenadrine citrate (Norflex) have established histories of success in treating patients with muscle spasms associated with acute, painful musculoskeletal conditions. They were initially approved by the FDA several years apart but are often used interchangeably due to their similar effects on the central nervous system.

The effectiveness of cyclobenzaprine and orphenadrine in alleviating muscle spasm was directly studied in a double-blind clinical trial; both drugs demonstrated comparable efficacy in relieving symptoms of muscle spasm as well as similar safety profiles. None of the different metrics studied to measure efficacy differed considerably between patients receiving Norflex and those receiving Flexeril.

A review indicated that cyclobenzaprine is effective from the first week of treatment, that its side effect profile is relatively mild compared to many other muscle relaxants, and it is generally well-tolerated. Its optimal dose for most adults is 5-10 mg taken three times daily.

On the other hand, a meta-analysis suggested that orphenadrine seems more effective than placebo at relieving pain related to muscle spasms. It's typically considered when first-line treatments fail or aren't tolerated by patients. Orphenadrine has robust data supporting its use as an adjunctive treatment alongside physical therapy and rest for symptomatic relief. Nonetheless, due to its unique pharmacology, Norflex may be an ideal choice for patients who did not respond well to other muscle relaxants or have specific needs such as avoiding common side effects like sedation.

abstract image of a researcher studying a bottle of drug.

At what dose is Flexeril typically prescribed?

Oral dosages of Flexeril range from 5–10 mg three times a day, but for most people with muscle spasms, 5 mg three times a day is enough. In the elderly population or those with liver impairment, it's advisable to start at the lower end of the dosage spectrum. After several weeks if there is no response, the dosage may be increased under medical supervision. The maximum daily dose should not exceed 30 mg in any case.

The suggested starting dose for Norflex is one 100mg tablet twice per day - morning and night. For some patients, one tablet per day will suffice. If more relief is needed after five days of therapy, your doctor might increase this to two tablets taken four times a day (8 tablets). However, taking more than eight tablets in a single twenty-four-hour period can result in an overdose which may lead to serious health issues.

At what dose is Norflex typically prescribed?

Norflex treatment typically begins at a dosage of 100 mg given twice daily. The dose can be increased to a maximum of 400 mg/day, divided into two doses and spaced approximately 12 hours apart if necessary, depending on the patient's response and tolerance. If there is no noticeable improvement in muscle spasms or pain after several weeks of treatment at the starting dose, your doctor may consider testing an increase to this higher dosage. It should be noted that each dose adjustment should only be made under medical supervision as Norflex can cause side effects such as dry mouth, blurred vision and dizziness.

What are the most common side effects for Flexeril?

Common side effects of Flexeril (cyclobenzaprine) include:

  • Drowsiness or sleepiness
  • Dry mouth
  • Fatigue and general weakness
  • Headache
  • Dizziness
  • Nausea, stomach pain, constipation or diarrhea

On the other hand, Norflex (orphenadrine) can cause:

  • Blurred vision
  • Dry mouth
  • Urinary retention and/or constipation
  • Heart palpitations -Nervousness or anxiety
    -Increased heart rate

Although these medications have different side effect profiles, both may potentially lead to more serious complications like hallucinations, confusion, and unusual changes in mood or behavior. Always consult with your healthcare provider before starting a new medication.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Flexeril?

Flexeril and Norflex are muscle relaxants that work differently but can have similar side effects. For Flexeril, serious side effects could include:

  • Allergic reactions such as difficulty breathing; swelling of your face, lips, tongue or throat
  • Chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating
  • Sudden numbness or weakness on one side of the body
  • Sudden headaches, confusion or speech balance problems
  • Unusual thoughts or behavior leading to self-harm

For Norflex in rare cases it may lead to severe allergic reactions like itching/swelling (especially of the face/tongue/throat), severe dizziness and trouble breathing. Other extreme symptoms might include:

  • Fast/irregular heartbeat
  • Fainting
  • Mental/mood changes including hallucinations/confusion

In both instances if any unusual conditions occur after taking these medications you should consult with a healthcare professional immediately.

What are the most common side effects for Norflex?

Norflex, a muscle relaxant often prescribed for acute musculoskeletal conditions, can potentially lead to the following side effects:

  • Dry mouth or throat
  • Blurred vision
  • Nausea, stomach upset or constipation
  • Difficulty in sleeping (insomnia)
  • Rapid heartbeat (tachycardia)
  • Feeling nervous or anxious
  • Confusion or agitation
  • Skin rash
  • Dizziness and headache It's less common but there could be weight changes and increased frequency of urination. Muscle pain is unlikely with Norflex as it's used precisely to treat such discomforts. As always, ensure you consult your healthcare provider if any of these symptoms persist.

Are there any potential serious side effects for Norflex?

While Norflex is generally well-tolerated, it can sometimes lead to severe side effects in certain individuals. If you notice any of the following symptoms after starting Norflex, seek immediate medical attention:

  • Signs of an allergic reaction such as hives; difficulty breathing or swallowing; swelling of your face, lips, tongue or throat.
  • Experiencing a slow heart rate or weak pulse
  • A light-headed feeling like you might pass out
  • Unusual thoughts or behavior
  • Seeing hallucinations (seeing things that are not there)
  • Little to no urination and/or painful urination
  • Fever accompanied by confusion and a stiff neck Remember to always consult with your healthcare provider before making changes to your medication regimen.

Contraindications for Flexeril and Norflex?

Both Flexeril and Norflex, along with most other muscle relaxant medications, may cause drowsiness or lightheadedness. If you experience these symptoms excessively or if they persist, please seek immediate medical attention.

Neither Flexeril nor Norflex can be taken if you are using, or have been using monoamine oxidase (MAO) inhibitors in the last 14 days. These drugs can interact dangerously with both muscle relaxants causing severe side effects like high fever and seizures. Always inform your doctor about all the medications you're currently taking; MAOIs will require a period of about 2 weeks to clear from your system before starting either Flexeril or Norflex to prevent harmful interactions.

How much do Flexeril and Norflex cost?

For the brand name versions of these drugs:

  • The price for 60 tablets of Flexeril (10 mg) averages around $750, which works out to approximately $25/day.
  • The cost for a 30 tablet pack of Norflex (100 mg) is about $150, working out to roughly $5/day.

Thus, if you are taking the standard dosage for Flexeril (i.e., 10 mg three times per day), then brand-name Norflex is less expensive on a per-day treatment basis. Please note that cost should not be your primary consideration in determining which of these drugs is right for you.

The generic versions significantly lower costs:

  • Cyclobenzaprine HCl (Flexeril's generic equivalent) comes in packs ranging from 20 tablets upwards and costs between $0.50 and $1.25 per day depending on your dose.
  • Orphenadrine citrate (generic Norflex) can also come in at least packs of twenty or more with daily costs averaging from as low as under a dollar up to about two dollars depending upon your specific dosage requirements.

Popularity of Flexeril and Norflex

Cyclobenzaprine, under the brand name Flexeril among others, was estimated to have been prescribed to about 16 million people in the US in 2020. Cyclobenzaprine accounted for just over 22% of muscle relaxant prescriptions in the US. Although it is not classified as a narcotic or an opioid, cyclobenzaprine has been generally increasing in prevalence since its approval by FDA.

On the other hand, Orphenadrine Citrate including brand versions such as Norflex was prescribed to around 1 million people in USA during same year. In terms of overall muscle relaxant prescriptions within America, orphenadrine citrate accounts for just below 5%. The usage of this medication has remained approximately steady over recent years despite being on market longer than cyclobenzaprine.


Both Flexeril (cyclobenzaprine) and Norflex (orphenadrine) have a long history of use in patients with muscle spasms, and they are supported by numerous clinical studies indicating that they are more effective than placebo treatments. In some cases, these drugs may be combined with other medication, but this is subject to careful consideration by a physician due to potential drug interactions. Both cyclobenzaprine and orphenadrine work primarily on central nervous system to provide skeletal muscle relaxation.

Flexeril is often prescribed as the first-line treatment for acute painful musculoskeletal conditions, whereas Norflex might usually be considered as an alternative when patients do not respond well to initial therapy or have contraindications for using cyclobenzaprine like arrhythmia or hyperthyroidism.

Both medications are available in generic form which represents significant cost savings especially for those who must pay out of pocket. The therapeutic effects of both Flexeril and Norflex could take up to several days depending upon individual patient response.

The side effect profile between two drugs varies slightly; common side effects include drowsiness, dry mouth and constipation. However, anticholinergic side effects like blurred vision or urinary retention may occur less frequently with Flexeril compared to Norflex. For both medications, patients should monitor their reaction closely when starting treatment because excessive sedation can happen at the beginning stage which requires immediate medical attention.