What is Norflex (orphenadrine citrate)?

From the Guidelines

Norflex, also known as orphenadrine, should be used with caution in patients due to its anticholinergic properties and potential for adverse effects, particularly in the elderly and those with certain medical conditions, as noted in a 2021 consensus statement by the Society for Perioperative Assessment and Quality Improvement (SPAQI) 1. When considering the use of Norflex, it is essential to weigh the potential benefits against the risks, particularly in patients with pre-existing conditions such as tachycardia, cardiac decompensation, coronary insufficiency, and cardiac arrhythmias. The medication's mechanism of action, although not fully understood, is thought to involve anticholinergic properties, which can lead to adverse effects like confusion, anxiety, tremors, urinary retention, dry mouth, constipation, and cardiovascular instability. Some key points to consider when prescribing Norflex include:

• Contraindications: gastrointestinal tract obstruction, stenosing peptic ulcer disease, prostatic hypertrophy or bladder outlet obstruction, glaucoma, and myasthenia gravis
• Potential interactions: potentiation of anticholinergic effects when used with other medications that have anticholinergic properties
• Special precautions: use with caution in the elderly and patients with certain medical conditions, as noted above According to the 2021 SPAQI consensus statement, Norflex is commonly administered both preoperatively and perioperatively, highlighting its potential utility in the management of muscle pain and spasms in the perioperative period 1. However, it is crucial to carefully evaluate the risks and benefits of using Norflex in individual patients, taking into account their unique medical history and current health status.

From the FDA Drug Label

CLINICAL PHARMACOLOGY The mode of therapeutic action has not been clearly identified, but may be related to its analgesic properties. Orphenadrine citrate does not directly relax tense muscles in man. Orphenadrine citrate also possesses anticholinergic actions. INDICATIONS AND USAGE Orphenadrine citrate is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute painful musculoskeletal conditions. The main use of Norflex, also known as orphenadrine, is as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute painful musculoskeletal conditions.

• Key points about Norflex include:
  • It has analgesic properties.
  • It does not directly relax tense muscles in humans.
  • It has anticholinergic actions. 2 2

From the Research

Norflex Overview

• Norflex, also known as orphenadrine, is a medication with central and peripheral anticholinergic properties 3, 4.
• It is commonly prescribed as a muscle relaxant and as an adjunct to antipsychotic medications to prevent parkinsonism 4.

Toxicity and Side Effects

• Ingestion of 2 to 3 g orphenadrine in an adult has been associated with fatality 3.
• Orphenadrine intoxication can cause convulsions, hemodynamic instability, severe rhabdomyolysis, and persistent nausea 3.
• Central anticholinergic toxicity can manifest as hallucinations and severe agitation, particularly in children 4.
• Orphenadrine can cause profound toxicity in children after ingestion of small doses 4.

Anticonvulsant Properties

• Orphenadrine has been shown to elevate the electrical seizure threshold in mice 5.
• It can enhance the anticonvulsant activity of certain antiepileptic drugs, such as valproate, without affecting their free plasma levels 5.
• However, orphenadrine fails to enhance the protective activity of other antiepileptic drugs, including carbamazepine, phenytoin, and phenobarbital 5.