The muscarinic receptor antagonist propiverine used for therapy of overactive bladder undergoes first pass metabolism, leading to several active metabolites, which affect muscarinic receptors and L-type Ca²⁺ channels with different potencies. M-5, the major metabolite in blood, and M-6 can be synthesized as cis- and trans-isomers. We systematically investigated the pharmacodynamic profiles of the isomers on detrusor contractile function. In murine and porcine detrusor, the effects of the derivatives were examined on contractions induced by electric field stimulation (EFS), cumulatively increasing concentrations of carbachol or high KCl concentration. EFS contractions were concentration-dependently reduced by the M-5 and M-6 isomers although to a different extent. M-5 _cis was slightly more potent than M-5 _trans, but the differences did not reach statistical significance. M-6 _cis was significantly more potent than M-6 _trans . Responses to carbachol were antagonized by all compounds due to rightward shifts of the concentration-response curves, but only M-5 _trans also significantly reduced the maximum response. pK _B values obtained with Schild plot analysis indicated slightly higher potency for M-6 _cis than M-6 _trans . Ca²⁺ influx-dependent contractions elicited by K⁺ depolarization were less impaired by low concentrations of the M-6 isomers, but strongly suppressed by 100 μM of the M-5 isomers, suggesting an additional effect of the two M-5 isomers on Ca²⁺ influx. All investigated isomers of M-5 and M-6 are biologically active in reducing detrusor contraction in animal tissue. While M-5 _cis, M-6 _cis, and M-6 _trans possess surmountable or partially surmountable antagonistic properties at muscarinic receptors, M-5 _trans is a strong non-competitive antagonist. However, at higher concentration ranges, all four compounds seem to have additional effects on Ca²⁺ influx.