(S)-(+)-Dimethindene (maleate)

(S)-(+)-Dimethindene maleate, an enantiomer, is a potent M2-selective muscarinic receptor antagonist (pA2 = 7.86/7.74; pKi = 7.78). (S)-(+)-Dimethindene maleate shows lower affinities for the muscarinic M1 (pA2 = 6.83/6.36; pKi = 7.08), the M3 (pA2 = 6.92/6.96; pKi = 6.70) and the M4 receptors (pKi = 7.00), respectively. (S)-(+)-Dimethindene maleate also is a histamine H1 receptor antagonist (pA2 = 7.48).