Potent M3 muscarinic receptor antagonist that displays ~ 120-fold selectivity over M2 receptors (Ki values are 4.2, 19 and 490 nM for human M3, M1 and M2 receptors respectively). Exhibits > 250-fold bronchial selectivity; inhibits ACh-induced bronchoconstriction but not ACh-induced bradycardia (KB values are 3.3 and 170 nM for rat trachea M3 and rat right atria M2 receptors respectively).Synonyms:(aR)-a-Cyclopentyl-a-hydroxy-N-[1-(4-methyl-3-pentenyl)-4-piperidinyl]benzeneacetamide fumarateCAS Number:257603-40-0Molecular Formula:C24H36N2O2.C4H4O4Molecular Weight:500.63Appearance:White solidPurity:≥99% (HPLC)Solubility:DMSO to 100mM, ethanol to 50mM