Drugs   Degree of purity% DSC              Pharmacopoeial Melting point ºC DSC     mp Apparatus          Merk index Azelastine 99.97            99.00 -101.00* 222                   223                     225-229 Emedastine 98.97            98.50-101.00** 147                   149                      148-151 * Official BP 2011. ** Official USP 2011.

Table 2: Degree of purity and melting point of azelastine HCl and emedastine difumarate in drug substances by DSC, melting point apparatus, and pharmacopoeial.