Side Effects of Norflex (orphenadrine)

Does Norflex (orphenadrine) cause side effects?

Norflex (orphenadrine) is a skeletal muscle relaxant used to treat acute muscle aches, pain, or spasms.

The exact mechanism of action in relieving muscular aches or spasms is not completely understood. Norflex may reduce muscle spasms through actions on motor centers or the medulla in the brain. Norflex does not seem to have any direct relaxant effects on skeletal muscle.

Norflex is structurally related to the antihistamine diphenhydramine (Benadryl), however, its antihistamine activity is less than that of diphenhydramine. Norflex also has some local anesthetic effects. The brand name Norflex is discontinued in the U.S.

Common side effects of Norflex include

Serious side effects of Norflex include

Drug interactions of Norflex include dofetilide, because Norflex may cause an increase in blood levels of dofetilide by decreasing its breakdown and elimination by the liver.

  • Norflex may cause drowsiness.
  • Taking Norflex with other drugs that have similar central nervous system (CNS) depressant effects may increase the CNS depressant effects of Norflex.
  • Norflex may cause anticholinergic side effects such as dry mouth, dry eyes, constipation, confusion, and decreased urinary frequency.
  • Taking medications that also have anticholinergic effects increases the anticholinergic effect of Norflex.

Norflex should be avoided in pregnancy if possible. It is unknown if Norflex is secreted into breast milk. Consult your doctor before breastfeeding.

What are the important side effects of Norflex (orphenadrine)?

Side effects of orphenadrine include:

Rare but serious side effects include aplastic anemia and life threatening allergic reactions.

Norflex (orphenadrine) side effects list for healthcare professionals

Adverse reactions of orphenadrine are mainly due to the mild anti-cholinergic action of orphenadrine, and are usually associated with higher dosage. Dryness of the mouth is usually the first adverse effect to appear.

When the daily dose is increased, possible adverse effects include:

  • tachycardia,
  • palpitation,
  • urinary hesitancy or retention,
  • blurred vision,
  • dilatation of pupils,
  • increased ocular tension,
  • weakness,
  • nausea,
  • vomiting,
  • headache,
  • dizziness,
  • constipation,
  • drowsiness,
  • hypersensitivity reactions,
  • pruritus,
  • hallucinations,
  • agitation,
  • tremor,
  • gastric irritation, and rarely
  • urticaria and other dermatoses.

Infrequently, an elderly patient may experience some degree of mental confusion. These adverse reactions can usually be eliminated by reduction in dosage. Very rare cases of aplastic anemia associated with the use of orphenadrine tablets have been reported. No causal relationship has been established.

Rare instances of anaphylactic reaction have been reported associated with the intramuscular injection of Norflex (orphenadrine) Injection.

Does Norflex (orphenadrine) cause addiction or withdrawal symptoms?

Drug Abuse And Dependence

Orphenadrine has been chronically abused for its euphoric effects. The mood-elevating effects may occur at therapeutic doses of orphenadrine.

What drugs interact with Norflex (orphenadrine)?

No information provided.


Norflex (orphenadrine) is a skeletal muscle relaxant used to treat acute muscle aches, pain, or spasms. Common side effects of Norflex include increased heart rate, itching, dizziness, drowsiness, headache, confusion, urinary retention, constipation, nausea, vomiting, dry mouth, dry eyes, upset stomach, weakness, and nasal congestion. Norflex should be avoided in pregnancy if possible. It is unknown if Norflex is secreted into breast milk.

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