TABLE 1

Comparison of the equilibrium and kinetic parameters of M₃ antagonists under nonphysiological and physiological conditions

Data are presented as the mean ± S.E. from a representative of three or more experiments.

Ligand	Nonphysiological			Physiological
Ligand	pK_i	k_off	t_1/2	pK_i	k_off	t_1/2
		min⁻¹	min		min⁻¹	min¹
Tiotropium	11.10 ± 0.02	0.0015 ± 0.0002	462	10.37 ± 0.04	0.015 ± 0.002	46.2
NVA237	10.30 ± 0.04	0.004 ± 0.002	173	9.59 ± 0.05	0.061 ± 0.003	11.4
[³H]NMS	10.45 ± 0.02	0.017 ± 0.001	41	9.51 ± 0.05	0.31 ± 0.03	2.24