Cyclobenzaprine
FlexerilPubChem CID 2895 · 3D model
Drag to rotate. Scroll or pinch to zoom.
Eases short-term muscle spasms by acting on the brainstem rather than the muscle or spinal cord, in a chemically TCA-like way that also brings TCA-like sedation and anticholinergic side effects — a different target entirely from baclofen's spinal-cord GABA-B action.
How it works
Exactly how cyclobenzaprine eases muscle spasms isn't fully known — even its own FDA label is upfront about that. What is known: unlike baclofen, also on this site, it doesn't act on muscle tissue itself or at the junction where nerves meet muscle. Instead it works higher up, in the brainstem region of the central nervous system, damping down the nerve signals that keep muscles in spasm — baclofen, by contrast, works lower down, at the spinal cord, through a specific calming-chemical receptor. Cyclobenzaprine is chemically a close cousin of older antidepressants called tricyclics, and it behaves like one in the body: sedating, and prone to the same dry-mouth, blurred-vision, anticholinergic side effects, and it's never combined with a class of drugs called MAO inhibitors because of a dangerous reaction risk.
What it’s used for
Used alongside rest and physical therapy to ease muscle spasms from short-term problems like a pulled muscle or back strain, and not meant to be taken for more than two or three weeks. It's not for the ongoing muscle stiffness caused by conditions like cerebral palsy or spinal cord disease — that's baclofen's territory, also on this site, which is approved specifically for that kind of longer-term spasticity.
- Mechanism
- Central (brainstem-level) skeletal muscle relaxant
- Drug class
- Small molecule
- Therapeutic area
- Neurology / Muscle Relaxant