Cyclobenzaprine is a skeletal muscle relaxant that also has sedative properties. It has been shown to antagonize muscarinic receptors (Kis = 25, 60, and 6 nM for M1, M2, and M3, respectively), serotonin 5-HT2 receptors (Kis = 56 and 330 nM for 5-HT2C and 5-HT2B, respectively), and histamine H1 receptor (IC50 = 20 nM).