4. Anticholinergic drugs bind to cholinergic receptors. Acetylcholine is the end

Question

4. Anticholinergic drugs bind to cholinergic receptors. Acetylcholine is the endogenous substance that binds to cholinergic receptors. But inflammatory mediators (histamine, bradykinin, eicosanoids) also stimulate cholingergic receptors. What happens when cholinergic receptors are stimulated in the airways? Why would oral anticholinergic drugs such as the over-the-counter (OTC) antihistamine diphenhydramine (Benadryl) be dangerous for a patient with COPD but inhaled anticholinergic drugs such as Atrovent (ipratropium)be beneficial?

Explanation / Answer

The human airways are innervated via afferent and efferent autonomic nerves which regulate many aspects of airway function. When cholinergic receptors are stimulated in this airway, they cause mucus seretion, bronchoconstriction and bronchial vasodilation. This is because of release of acetylcholine from parasympathetic nerves activates post junctional muscarnic receptors present on airway submucosal glands,, smooth muscle amd blood vessels.

Inhaled drugs like Atrovert has slow and prolonged action and is widely used to prevent bronchioconstriction.Inhaled therapy contains anticholinergic drugs which relax airway smooth muscle by blocking cholinergic tone and beta 2 agonists which are nonspecific bronchodilators that work via sympathetic pathway. This shows great response to treat COPD, where as treating COPD with OTC drugs has found many side effects.

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