2-(Ethylammonio)-N-methylpyridinium dimethanesulphonate 2-Pyridineethanamine, N-methyl-, dimethanesulfonate 54856-23-4 5638-76-6 Betahistine mesilate Betahistine mesylate EINECS 259-377-7 Extovyl Meginalisk Melopat Merislon Riptonin