Reviewed on 11/15/2021

What Is Orphenadrine and How Does It Work?

Orphenadrine is a prescription medication used to treat Muscle Spasm and Pain. 

  • Orphenadrine is available under the following different brand names: Norflex

What Are Dosages of Orphenadrine?

Adult dosage

Injectable solution

  • 30mg/mL

Tablet, extended release

  • 100mg

Muscle Spasm & Pain

  • 100 mg orally every 12 hours or 
  • 60 mg IV/IM every 12 hours (switch to orally as soon as possible)

Dosage Considerations – Should be Given as Follows: 

See “Dosages”.

What Are Side Effects Associated with Using Orphenadrine?

Common side effects of Orphenadrine include:

  • dizziness, 
  • drowsiness, 
  • weakness, 
  • nausea, 
  • vomiting, 
  • dry mouth, and 
  • constipation

Serious side effects of Orphenadrine include:

  • hives, 
  • difficulty breathing, 
  • swelling of the face, lips, tongue, or throat, and
  • lightheadedness
  • painful or difficult urination
  • little or no urination, 
  • confusion, 
  • anxiety, 
  • agitation, 
  • tremors, 
  • hallucinations, 
  • pounding heartbeats, and
  • fluttering in the chest

Rare side effects of Orphenadrine include:

  • none 
This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Orphenadrine?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them.  Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first

  • Orphenadrine has severe interactions with no other drugs.
  • Orphenadrine has serious interactions with at least 11 other drugs. 
  • Orphenadrine has moderate interactions with at least 203 other drugs.
  • Orphenadrine has minor interactions with the following drugs:

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drugs interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use.  Keep a list of all your medications with you, and share this information with your doctor and pharmacist.  Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Orphenadrine?


Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Orphenadrine?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Orphenadrine?”


  • Use caution in patients with diarrhea, partial obstructive uropathy, open-angle glaucoma, cardiovascular disease, hepatic/renal impairment, thyrotoxicosis, history of drug abuse or acute alcoholism
  • Some patients may experience transient episodes of light-headedness, dizziness or syncope; drug may impair ability of patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle; ambulatory patients should be cautioned
  • May take with food to avoid stomach upset
  • Use with caution in patients with tachycardia, cardiac decompensation, coronary insufficiency, cardiac arrhythmias
  • Injectable form contains sulfites, & precipitates anaphylactic-type reactions in sensitive or asthmatic individuals
  • Safety of continuous long-term therapy not established; if orphenadrine is prescribed for prolonged use, periodic monitoring of blood, urine and liver function values is recommended
  • Drug interaction overview
    • Confusion, anxiety and tremors have been reported in patients receiving propoxyphene and orphenadrine concomitantly; as symptoms may be simply due to an additive effect, reduction of dosage and/or discontinuation of one or both agents is recommended in such cases

Pregnancy and Lactation

  • Use with caution during pregnancy if benefits outweigh risks.
  • No data available for use during lactation or breast feeding

Health Solutions From Our Sponsors