Selectivity of antimuscarinic compounds for muscarinic receptors of human brain and heart.

Seven antimuscarinic compounds, used mostly for the treatment of extrapyramidal problems, were tested in vitro in radioligand binding assays for evidence of selectivity for two different pharmacological subtypes of the human muscarinic receptor, M1, a predominant form in brain, and M2, a predominant form in heart. Although biperiden, scopolamine, procyclidine, and benztropine showed significant selectivity in the in vitro assays, it is likely that in clinical practice biperiden would be the drug of choice to avoid any antimuscarinic effects on the heart.