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.

Norflex (Discontinued in the US)

GENERIC AVAILABLE: Yes

Yes

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.

The recommended dose is one 100 mg tablet by mouth twice daily in the morning and evening.

: 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.

It is not known whether orphenadrine is secreted into breast milk. Orphenadrine should be avoided in pregnancy if possible.

What preparations of orphenadrine-oral are available?

• Orphenadrine citrate tablets: 100 mg extended release
• Orphenadrine citrate solution for injection: 30 mg/ml

How should I keep orphenadrine-oral stored?

Tablets should be stored at room temperature, between 15 C and 30 C (59 F and 86 F).