Medically Reviewed on 5/19/2023

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:

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.


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Which 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:

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).


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.

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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.

Medically Reviewed on 5/19/2023
FDA Prescribing Information.