Answer
Inhaled ipratropium bromide widens the airways through local anticholinergic action on bronchial smooth muscle, preventing the rise in intracellular calcium caused by acetylcholine acting at muscarinic receptors, rather than through systemic drug concentrations.
Sources for this answer
- Atrovent 250 UDVs, 1 ml / Atrovent UDVs, 2 mlBoehringer Ingelheim Limited · emc · SmPC §5.1 Pharmacodynamic properties · Version 18Document updated
Sources checked