Which intravenous medication may be used in severe acute asthma to reduce bronchospasm?

• A. IV magnesium sulfate
• B. IV antibiotics
• C. IV diuretics
• D. IV antihistamines

Answer: (A)

Intravenous magnesium sulfate reduces bronchospasm by relaxing bronchial smooth muscle, primarily through blocking calcium entry into cells. This calcium antagonism decreases smooth muscle contraction, leading to bronchodilation, and it may also help stabilize membranes and dampen release of inflammatory mediators. In severe acute asthma, it’s added as an adjunct when standard therapy with inhaled beta-agonists and systemic steroids hasn’t fully controlled the attack, helping to improve airflow and sometimes reduce the need for hospitalization.

Antibiotics don’t address the immediate bronchospasm since they target infection rather than airway smooth muscle. Diuretics remove fluid but don’t relieve bronchoconstriction. Antihistamines have limited effect on acute bronchospasm in asthma and aren’t used to treat the emergency airway obstruction.