ACLIDINIUM BROMIDE IS AN ANTICHOLINERGIC, SYNTHETIC, QUATERNARY AMMONIUM COMPOUND WITH SPECIFICITY FOR MUSCARINIC RECEPTORS. IT HAS SIMILAR AFFINITY TO THE SUBTYPES OF MUSCARINIC RECEPTORS M1 TO M5. IN THE AIRWAYS, IT EXHIBITS PHARMACOLOGICAL EFFECTS THROUGH INHIBITION OF M3 RECEPTOR AT THE SMOOTH MUSCLE LEADING TO BRONCHODILATION. PREVENTION OF ACETYLCHOLINE-INDUCED BRONCHONCONSTRICTION EFFECTS WAS DOSE-DEPENDENT AND LASTED LONGER THAN 24 HOURS. THE BRONCHODILATION FOLLOWING INHALATION OF ACLIDINIUM BROMIDE IS PREDOMINANTLY A SITE-SPECIFIC EFFECT.