Skip to Content


Generic Name: Orphenadrine Citrate
Class: Skeletal Muscle Relaxants, Miscellaneous
VA Class: MS200
CAS Number: 341-69-5

Medically reviewed by Last updated on Nov 19, 2018.


See also: Emgality

Skeletal muscle relaxant; tertiary amine antimuscarinic.a b c k

Uses for Norflex

Muscular Conditions

Used alone or in combination with aspirin and caffeine as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions.a b c k

If pharmacologic therapy is required for acute low back pain (usually a benign and self-limiting condition105 106 108 ), an analgesic (e.g., acetaminophen, NSAIA) generally is recommended.104 105 106 108 117 Skeletal muscle relaxants may be used alone or in combination with analgesics for short-term relief; however, consider high incidence of adverse effects (e.g., CNS effects).104 106 107 108 Use skeletal muscle relaxants with caution and weigh risks against benefits.104 106 107 108

Various skeletal muscle relaxants appear to have comparable efficacy for low back pain relief.103 104 106 108

Norflex Dosage and Administration


Administer orally or by IV or IM injection.a b c k

Switch from parenteral to oral therapy as soon as possible.c

Oral Administration

Administer orphenadrine citrate extended-release tablets orally twice daily.b c

Administer orphenadrine citrate fixed-combination tablets (with aspirin and caffeine) orally 3 or 4 times daily.k

IV Administration

Place patient in supine position during and for 5–10 minutes following IV injection.c (See CNS Effects under Cautions.) To minimize adverse reactions, assist patient from recumbent position.c

Rate of Administration

Administer IV over about 5 minutes.c


Available as orphenadrine citrate; dosage expressed in terms of the salt.a b


Muscular Conditions
Therapy with Extended-release Tablets

100 mg twice daily.a b

Therapy with Orphenadrine Fixed-combination Tablets

25–50 mg (in combination with aspirin 385–770 mg and caffeine 30–60 mg) 3 or 4 times daily.k

Parenteral Therapy
IV or IM

60 mg every 12 hours.a b

Cautions for Norflex


  • Glaucoma.a b k

  • Pyloric or duodenal obstruction.a b k

  • Stenosing peptic ulcers.a b

  • Prostatic hypertrophy or obstruction of the bladder neck.a b k

  • Cardiospasm (megaesophagus).a b

  • Myasthenia gravis.a b k

  • Known hypersensitivity to orphenadrine or any ingredient in the formulation.a b k



CNS Effects

Transient episodes of light-headedness, dizziness, or syncope reported.a b k

Performance of activities requiring mental alertness or physical coordination (e.g., operating machinery, driving a motor vehicle) may be impaired.a b k

Sensitivity Reactions

Sulfite Sensitivity

Injectable formulation contains sodium bisulfite, which can cause allergic-type reactions, including anaphylaxis and life-threatening or less severe asthmatic episodes, in certain susceptible individuals.100 a b

Overall prevalence of sulfite sensitivity in the general population unknown but probably low; such sensitivity appears to occur more frequently in asthmatic than in nonasthmatic individuals.100 a b

General Precautions

Adequate Patient Monitoring

Safety of continuous therapy not established.a b k Perform periodic blood, urine, and liver function tests during prolonged orphenadrine therapy.c k

Cardiac Effects

Possible tachycardia and palpitation; may be associated with increased dosages.a b Use with caution in patients with tachycardia, cardiac decompensation, coronary insufficiency, or cardiac arrhythmias.a b

Use of Fixed Combinations

When orphenadrine is used in fixed combination with aspirin and caffeine, consider the cautions, precautions, and contraindications associated with each agent in the combination.k

Specific Populations


Category C.a b


Not known whether orphenadrine is distributed into milk; use with caution.c

Pediatric Use

Safety and efficacy not established in children <12 years of age.c

Common Adverse Effects

Dry mouth,a b k tachycardia,a b k palpitation,a b k urinary hesitancy or retention,a b k blurred vision,a b k dilatation of pupils,a b k increased intraocular pressure,a b k weakness,a b k nausea,a b k vomiting,a b k headache,a b k dizziness,a b k constipation,a b k drowsiness.a b k

Interactions for Norflex

Specific Drugs





Potential additive CNS effectsa b c k

Reduce dosage and/or discontinue one or both agents if adverse CNS effects develop during concomitant therapya b c k

Norflex Pharmacokinetics



Readily absorbed following oral administration.c



Distribution not fully characterized in humans.c In animals, detected in all organs, especially those with greatest perfusion (e.g., lungs).c

Orphenadrine may cross the placenta; not known whether distributed into milk.c



Almost completely metabolized to at least 8 metabolites; however, metabolic fate not fully determined.c

Elimination Route

Eliminated principally in urine as metabolites and, in small amounts, as unchanged drug.c


Approximately 14 hours.c





15–30°C.b c k



15–30°C.a b c Do not freeze; protect from light.c


  • CNS depressant with skeletal muscle relaxant effects.c

  • Precise mechanism of action not known.a k Does not directly relax skeletal muscle;a b c k therapeutic action may be related to analgesic properties.a c k

  • May reduce skeletal muscle spasm, possibly through an atropine-like central action on cerebral motor centers or on the medulla.c

  • Exhibits postganglionic anticholinergic,a c antihistaminicc , and local anesthetic properties.c

Advice to Patients

  • Potential to impair mental alertness or physical coordination; use caution when driving or operating machinery until effects on individual are known.a b k

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as concomitant illnesses.a b k

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.a b k

  • Importance of informing patients of other important precautionary information.a b k (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Orphenadrine Citrate


Dosage Forms


Brand Names



Tablets, extended-release

100 mg*



Orphenadrine Citrate Tablets



30 mg/mL*



Orphenadrine Citrate Injection

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Orphenadrine Citrate Combinations


Dosage Forms


Brand Names




25 mg with Aspirin 385 mg and Caffeine 30 mg*



Orphenadrine Citrate, Aspirin, and Caffeine Tablets


50 mg with Aspirin 770 mg and Caffeine 60 mg*

Norgesic Forte (scored)


Orphenadrine Citrate, Aspirin, and Caffeine Tablets

AHFS DI Essentials™. © Copyright 2019, Selected Revisions November 18, 2012. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.


Only references cited for selected revisions after 1984 are available electronically.

100. Food and Drug Administration. Sulfiting agents; labeling in drugs for human use; warning statements. [21 CFR Part 201] Fed Regist. 1986; 51:43900-5.

103. See S, Ginzburg R. Skeletal muscle relaxants. Pharmacotherapy. 2008; 28:207-13.

104. van Tulder MW, Touray T, Furlan AD et al. Muscle relaxants for non-specific low back pain. Cochrane Database Syst Rev. 2003; :CD004252.

105. Roelofs PD, Deyo RA, Koes BW et al. Non-steroidal anti-inflammatory drugs for low back pain. Cochrane Database Syst Rev. 2008; :CD000396.

106. Chou R, Qaseem A, Snow V et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007; 147:478-91.

107. Institute for Clinical Systems Improvement. Health care guideline: adult acute and subacute low back pain. 15th ed. Bloomington, MN; 2012 Jan. From the ICSI website

108. Toth PP, Urtis J. Commonly used muscle relaxant therapies for acute low back pain: a review of carisoprodol, cyclobenzaprine hydrochloride, and metaxalone. Clin Ther. 2004; 26:1355-67.

117. Boothby LA, Doering PL, Hatton RC. Carisoprodol: a marginally effective skeletal muscle relaxant with serious abuse potential. Hosp Pharm. 2003; 38:337-45.

a. Hospira, Inc. Norflex (orphenadrine citrate) injection prescribing information. Lake Forest, IL; 2004 Jul.

b. 3M Pharmaceuticals. Norflex (orphenadrine citrate) extended-release tablets and injection prescribing information. Northridge, CA; 2000 Jul.

c. AHFS drug information 2007. McEvoy GK, ed. Orphenadrine Citrate. Bethesda, MD: American Society of Health-System Pharmacists; 2007:1398-9.

k. 3M Pharmaceuticals. Norgesic and Norgesic Forte tablets prescribing information. Northridge, CA; 1998 May.