Magnesium sulfate helps in acute asthma exacerbations by what mechanism?

• A. Relaxing effect on smooth muscles and stabilizes many inflammatory mediators
• B. Vasodilation
• C. Increase mucus clearance
• D. Decrease heart rate

Answer: (A)

Magnesium sulfate works in acute asthma mainly by relaxing airway smooth muscle and dampening inflammatory mediator activity. It acts as a calcium antagonist in airway smooth muscle, blocking calcium entry into the cells. With less intracellular calcium, the muscles around the airways relax, producing bronchodilation and easing airflow. It also helps stabilize mast cell membranes, reducing release of mediators like histamine and leukotrienes that contribute to bronchoconstriction, and it can reduce acetylcholine release, diminishing bronchial hyperreactivity. This combination addresses the two main problems in an acute asthma attack: acute narrowing of the airways and ongoing inflammation.

That’s why the best description is a relaxing effect on smooth muscles and stabilization of inflammatory mediators. It isn’t primarily about vasodilation in this context, it doesn’t directly increase mucus clearance, and it doesn’t aim to slow the heart rate.