Generic Name: orphenadrine
Brand Name: Norflex (Discontinued in the U.S.)
Drug Class: Skeletal Muscle Relaxants
What is oral orphenadrine, and what is it used for?
Orphenadrine is an oral central acting skeletal muscle relaxant that is used for the treatment of acute muscle aches, pain, or spasms. The exact mechanism of action in relieving muscuar aches or spasms is not completely understood. Orphenadrine may reduce muscle spasms through actions on motor centers or the medulla in the brain. Orphenadrine does not seem to have any direct relaxant effects on skeletal muscle.
Orphenadrine is structurally related to the antihistamine diphenhydramine (Benadryl), however, its antihistamine activity is less than that of diphenhydramine. Orphenadrine also has some local anesthetic effects. The FDA approved Orphenadrine in 1959.
What are the side effects of oral orphenadrine?
Side effects of orphenadrine include:
- increased heart rate,
- itching,
- dizziness,
- drowsiness,
- headache,
- confusion,
- urinary retention,
- constipation,
- nausea,
- vomiting,
- dry mouth,
- dry eyes,
- upset stomach,
- weakness, and
- nasal congestion.
Rare but serious side effects include aplastic anemia and life threatening allergic reactions.
What is the dosage for oral orphenadrine?
The recommended dose is one 100 mg tablet by mouth twice daily in the morning and evening.

SLIDESHOW
Rheumatoid Arthritis Exercises: Joint-Friendly Workouts See SlideshowWhich drugs interact with oral orphenadrine?
Orphenadrine may cause an increase in blood levels of dofetilide (Tikosyn) by decreasing its breakdown and elimination by the liver.
Orphenadrine may cause drowsiness. Taking orphenadrine with other drugs that have similar CNS depressant effects may increase the CNS depressant effects of orphenadrine.
Orphenadrine may cause anticholingeric side effects such as:
- dry mouth,
- dry eyes,
- constipation,
- confusion, and
- decreased urinary frequency.
Taking medications that also have anticholingeric effects increases the anticholinergic effect of orphenadrine.
Pregnancy and breastfeeding
It is not known whether orphenadrine is secreted into breast milk. Orphenadrine should be avoided in pregnancy if possible.
What else should I know about oral orphenadrine?
What preparations of oral orphenadrine are available?
- Orphenadrine citrate tablets: 100 mg extended release
- Orphenadrine citrate solution for injection: 30 mg/ml
How should I store oral orphenadrine?
Tablets should be stored at room temperature, between 15 C and 30 C (59 F and 86 F).
Health News
- AHA News: This Tick Season, Beware the Tiny Bugs That Can Carry Lyme Disease – a Danger to the Heart
- Ticks Can Take a Licking From Really Tough Weather
- Drug Might Help Slow Nearsightedness in Kids
- Does Your Kid Need a Summer Vacation From Smartphones?
- Get in the Swim: Summer Pool Safety Tips
More Health News »
Summary
Orphenadrine (The brand Norflex has been discontinued in the US) is a prescription drug used to treat acute muscle aches, pains, or spasms. Side effects, drug interactions, warnings, precautions, dosing, storage, pregnancy, and breastfeeding safety information is included.
Multimedia: Slideshows, Images & Quizzes
-
Muscle Cramps (Charley Horse) and Muscle Spasms
What are the differences between muscle spasms and cramps? Learn about the causes of muscle spasms and cramps (charley horse) in...
-
Pain Management: Signs Your Muscle Pain Is Something Else
Could your achy muscles be a sign of more than a tough workout? Learn when a twinge might warrant a visit to the doctor's office.
-
Chronic Pain Syndrome: Treatment and Management for CPS
Do you suffer from excruciating pain? What is chronic pain syndrome (CPS)? See causes, symptoms and treatment options, including...
-
Pain Quiz: Test Your IQ of Pain
Is pain all in the brain? Take the Pain Quiz to learn everything you've ever wanted to know about the unpleasant sensation we...
-
Healthy Aging: Causes of Muscle Weakness
From aging to illness, many things can cause your muscles to get weaker. Learn about the causes and what you can do to make it...
-
Leg Pain: Causes and Treatments for Aching Calf, Thighs, and Muscles
Leg, calf and thigh pain are symptoms of conditions that may involve the muscles, nerves, and more. Sensations like tingling,...
-
How Does Acupuncture Work? Benefits, Needles, Definition
What is acupuncture? How does acupuncture work? Does acupuncture hurt? Learn various acupuncture points, the definition of...
-
Muscle Cramps: Foods That Help and Prevent Cramping
One way to prevent muscle cramps is to get enough of these nutrients: potassium, sodium, calcium, and magnesium. They’re called...
-
Neck Pain: Causes of Stiffness, Muscle Spasms, Treatment, and Relief
What causes chronic neck pain? If you have poor posture, bad sleep habits, or spine problems, these issues can lead to a stiff...
-
Causes of Muscle Twitches and Spasms
Sometimes your muscles seem to have a mind of their own. WebMD explains what could be behind your twitches, spasms, and cramps.
Related Disease Conditions
-
Muscle Spasms
Muscle spasms are involuntary muscle contractions that come on suddenly and are usually quite painful. Dehydration, doing strenuous exercise in a hot environment, prolonged muscle use, and certain diseases of the nervous system may cause muscle spasms. Symptoms and signs of a muscle spasm include an acute onset of pain and a possible bulge seen or felt beneath the skin where the muscle is located. Gently stretching the muscle usually resolves a muscle spasm.
-
Muscle Cramps
Muscle cramps are involuntarily and forcibly contracted muscles that do not relax. Extremely common, any muscles that have voluntary control, including some organs, are subject to cramp. Since there is such variety in the types of muscle cramps that can occur, many causes and preventative medications are known. Stretching is the most common way to stop or prevent most muscle cramps.
-
Lower Back Pain (Lumbar Spine Pain)
There are many causes of back pain. Pain in the low back can relate to the bony lumbar spine, discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis, and abdomen, and the skin covering the lumbar area.
-
Pain Management
Pain management and treatment can be simple or complex, according to its cause. There are two basic types of pain, nociceptive pain and neuropathic pain. Some causes of neuropathic pain include: complex regional pain syndrome, interstitial cystitis, and irritable bowel syndrome. There are a variety of methods to treat chronic pain, which are dependant on the type of pain experienced.
-
How Can You Tell If You Have Nerve Pain or Muscle Pain?
If the pain started after an injury and it's a dull ache, it's likely muscle pain. If your pain seemed to come out of nowhere or it's been ongoing, and it feels like your skin is on fire, you're likely experiencing nerve pain.
-
Is My Muscle Pulled or Strained?
A pulled muscle is sometimes used as a colloquial term for a strain of moderate severity. A muscle becomes strained when it’s twisted, pulled, or torn in two.
-
Muscle Pain (Myofascial Pain Syndrome)
Muscle pain (myofascial pain syndrome) is muscle pain in the body's soft tissues due to injury or strain. Symptoms include muscle pain with tender points and fatigue. Treatment usually involves physical therapy, massage therapy, or trigger point injection.
-
How Can I Relieve Muscle Soreness?
Here are 11 different ways to relieve muscle soreness at home following an intense workout or rigorous physical activity.
-
Muscle Cramps: Treatment
Muscle cramps cannot be stopped instantly with injections or pills, but some methods can be useful to relieve them which include stretching, massage, application of heat and cold, walking and taking B vitamins.
-
What Is the Best Thing for Sore Muscles?
Exercise may be vital for overall health and longevity, but it comes with pains and sprains. After a robust exercise session, your muscles may get sore or stiff. Slight soreness is a normal response to exercise, but there are good and bad soreness. Soreness should last for a day or two; if it lasts for more than 2 days along with signs of persistent pain, black-and-blue hued bruising, and numbness, then immediately consult a physician.
Treatment & Diagnosis
- Pain FAQs
- Drugs: Buying Prescription Drugs Online Safely
- Drugs: The Most Common Medication Errors
- Medication Disposal
- Dangers of Mixing Medications
- Is There a Direct Relationship Between Sinusitis and Muscle Pain?
- What Causes Rectal Muscle Spasms?
- Can Diabetes Cause Muscle Pain?
- Generic Drugs, Are They as Good as Brand-Names?
Medications & Supplements
Prevention & Wellness
Health Solutions From Our Sponsors

Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.