Cyclobenzaprine is not an NSAID. It is a centrally acting skeletal muscle relaxant, a completely different class of drug. While both cyclobenzaprine and NSAIDs like ibuprofen or naproxen are commonly prescribed for musculoskeletal pain, they work through entirely different mechanisms and produce different effects in your body.
How Cyclobenzaprine Actually Works
Cyclobenzaprine (sold under the brand name Flexeril, among others) is a tricyclic amine salt that acts in your central nervous system, specifically in the brain stem. Its job is to reduce muscle hyperactivity by dialing down the signals that keep muscles tense and in spasm. It influences both types of motor nerve pathways that control muscle tone, which is why it’s effective at loosening tight, spasming muscles.
Chemically, cyclobenzaprine is closely related to tricyclic antidepressants like amitriptyline and imipramine. It also blocks certain serotonin receptors, which contributes to its antispasmodic effect. This brain-based mechanism is why drowsiness and dry mouth are its most common side effects, not stomach irritation.
What Makes NSAIDs a Different Drug Class
NSAIDs, or nonsteroidal anti-inflammatory drugs, include familiar medications like ibuprofen (Advil, Motrin) and naproxen (Aleve). Their defining mechanism is inhibiting an enzyme called cyclooxygenase, which your body uses to produce chemicals that cause inflammation, pain, and fever. That’s why NSAIDs can reduce swelling and bring down a fever, two things cyclobenzaprine cannot do.
The key distinction: NSAIDs target inflammation at the site of injury, while cyclobenzaprine targets muscle tension signals in the brain. An NSAID won’t relax a muscle spasm, and cyclobenzaprine won’t reduce swelling or lower a fever.
Different Side Effect Profiles
Because these drugs work in completely different parts of your body, their side effects look nothing alike. Cyclobenzaprine’s most notable side effects are central nervous system effects: drowsiness, dizziness, and dry mouth. In a clinical trial comparing ibuprofen alone to ibuprofen plus cyclobenzaprine for muscle strain, 42% of patients taking cyclobenzaprine reported central nervous system side effects at 24 hours, compared to just 18% of those on ibuprofen alone.
NSAIDs, by contrast, are more likely to cause stomach upset, heartburn, and in some cases ulcers or bleeding with prolonged use. They can also affect kidney function and raise blood pressure over time. These gastrointestinal and cardiovascular concerns are not typically associated with cyclobenzaprine.
Why They’re Often Prescribed Together
The confusion between these two drugs may stem from the fact that doctors frequently prescribe them at the same time. Because they work through completely separate mechanisms, combining them can address different aspects of musculoskeletal pain simultaneously.
A clinical trial of patients with acute low back pain and muscle spasm found that combining cyclobenzaprine with naproxen (an NSAID) produced less muscle spasm and tenderness, along with greater range of motion in the lower back, compared to naproxen alone. There were also trends toward faster pain relief and quicker return of function. The tradeoff was more side effects in the combination group, primarily drowsiness from the cyclobenzaprine.
That said, adding cyclobenzaprine to an NSAID doesn’t always help. A separate trial looking at acute muscle strain found that adding cyclobenzaprine to ibuprofen didn’t improve pain relief but did increase drowsiness and other central nervous system side effects. The benefit of combination therapy seems to depend on whether significant muscle spasm is part of the problem.
Quick Comparison
- Cyclobenzaprine: Muscle relaxant. Works in the brain stem to reduce muscle spasm and tension. Causes drowsiness. Does not reduce inflammation or fever.
- NSAIDs (ibuprofen, naproxen): Anti-inflammatory and pain-relieving drugs. Work at the site of injury by blocking inflammation. Can cause stomach irritation. Do not relax muscle spasms directly.
If you’ve been prescribed cyclobenzaprine, it’s specifically targeting muscle tightness and spasm. It works alongside, not instead of, anti-inflammatory medications. The two drug classes complement each other, but they are not interchangeable.