Cyclobenzaprine hydrochloride is a white, crystalline tricyclic amine salt with the empirical formula C20H21NHCl and a molecular weight of 311.9. It has a melting point of 217#C, and a pKa of 8.47 at 25#C. It is freely soluble in water and alcohol, sparingly soluble in isopropanol, and insoluble in hydrocarbon solvents. If aqueous solutions are made alkaline, the free base separates. Cyclobenzaprine HCl is designated chemically as 3-(5H -dibenzo[a,d] cyclohepten-5-ylidene)-N, N-dimethyl-1-propanamine hydrochloride, and has the following structural formula: