Final answer:
The adverse effect of mucolytic agents in the treatment of bronchitis is bronchospasm.
Step-by-step explanation:
The adverse effect of mucolytic agents in the treatment of bronchitis is bronchospasm. Bronchospasm is the constriction of the airways in the lungs, leading to difficulty breathing and wheezing. This adverse effect can be problematic for patients with bronchitis as it can further exacerbate their respiratory symptoms.