Ipratropium Bromide is a muscarinic antagonist, bronchodilator, N-Isopropyl salt of atropine. Target: mAChR Ipratropium bromide, a nonselective muscarinic antagonist, is widely prescribed for the treatment of chronic obstructive pulmonary disease (COPD). In anaesthetised guinea-pigs, bronchoconstriction induced by vagal nerve stimulation was potentiated by low doses of the antimuscarinic bronchodilator drug, ipratropium (0.01-1.0 g/kg); the maximum effect was obtained with 1.0 g/kg which doubled the bronchoconstriction. When the dose was increased above 1.0 g/kg potentiation no longer occurred; instead the vagally induced bronchoconstriction was antagonized [1, 2].