Norflex is a brand name for orphenadrine citrate, a prescription muscle relaxant used to treat painful muscle spasms and stiffness. It works in the brain rather than directly on muscles, making it a centrally acting muscle relaxant with mild pain-relieving properties. Norflex is typically prescribed alongside rest and physical therapy for acute musculoskeletal conditions like back strains, neck injuries, or muscle pulls.
How Norflex Works
Orphenadrine is classified as a centrally acting, non-opioid analgesic and muscle relaxant. Its exact mechanism isn’t fully understood, but it appears to act on pain perception in the brain rather than numbing muscles directly. It also has anticholinergic activity, meaning it blocks a chemical messenger called acetylcholine. This combination of effects helps reduce both the sensation of pain and the involuntary tightening of muscles that often accompanies injuries.
After taking a tablet, most people feel relief within about an hour. Each dose lasts roughly 4 to 6 hours, though the drug stays in your system longer, with a half-life of about 14 hours. This longer half-life is why the extended-release tablet only needs to be taken twice a day.
Standard Dosing
Norflex comes as a 100 mg extended-release tablet. The standard adult dose is one tablet in the morning and one in the evening. It’s designed for short-term use alongside other treatments like rest, stretching, or physical therapy. Norflex is not intended as a long-term solution for chronic pain conditions.
Common Side Effects
Most side effects stem from the drug’s anticholinergic properties. Dry mouth is usually the first thing people notice and the most frequently reported complaint. At higher doses, additional effects can appear: drowsiness, dizziness, blurred vision, constipation, nausea, and headache. Some people experience a faster heart rate or difficulty urinating.
Less common reactions include confusion, agitation, tremor, hallucinations, and skin reactions like itching or hives. The good news is that most of these side effects are dose-related. If they become bothersome, reducing the dose typically resolves them. For dry mouth specifically, sugarless gum, ice chips, or a saliva substitute can help.
Because Norflex can cause drowsiness and lightheadedness, it may impair your ability to drive or operate machinery. Alcohol and other sedating medications amplify this effect, so combining them increases the risk of excessive drowsiness or impaired coordination.
Who Should Avoid Norflex
Norflex’s anticholinergic effects make it a poor fit for people with certain conditions. Those with glaucoma (specifically the narrow-angle type), urinary retention, or gastrointestinal obstruction face a higher risk of complications because the drug can worsen all three. People with myasthenia gravis, a condition that causes muscle weakness, should also avoid it.
Risks for Older Adults
The American Geriatrics Society includes orphenadrine on its Beers Criteria list, a widely used guide to medications that are potentially inappropriate for adults 65 and older. The recommendation is straightforward: avoid it. Older adults are more susceptible to the anticholinergic side effects, particularly confusion, sedation, and dizziness. These increase the risk of falls and fractures. The society also notes that muscle relaxants like orphenadrine may not work well enough at doses older adults can safely tolerate, making the risk-benefit tradeoff unfavorable.
How Norflex Compares to Other Muscle Relaxants
Norflex belongs to the same general class as other centrally acting muscle relaxants like cyclobenzaprine (Flexeril) and methocarbamol (Robaxin). What sets it apart is its additional mild analgesic effect, so it addresses both the spasm and some of the pain simultaneously. However, its anticholinergic properties are more pronounced than some alternatives, which means a broader range of potential side effects like dry mouth and urinary issues.
Unlike opioid painkillers, orphenadrine does not carry the same risk of physical dependence or respiratory depression. It’s a non-opioid option, which makes it useful when a prescriber wants to avoid narcotic medications for musculoskeletal pain. That said, it’s still a short-term treatment. Muscle relaxants in general are intended for acute episodes lasting days to a few weeks, not for ongoing pain management.