In the adult severe asthma (2nd bundle), what is the magnesium sulfate dosage and infusion duration?

• A. 1 g in 100 mL over 10 min
• B. 2 g in 250 mL over 30 min
• C. 4 g in 100 mL over 16 min
• D. 2 g in 100 mL over 16 min

Answer: (D)

Magnesium sulfate is added in adult severe asthma as an IV bronchodilator when standard treatments aren’t enough. It works by blocking calcium entry into airway smooth muscle, helping it relax and improving airway caliber. In this protocol, the recommended regimen is 2 grams diluted in 100 mL and infused slowly over about 16 minutes. This slow infusion provides bronchodilation while minimizing common infusion-related side effects like flushing, hypotension, and hyporeflexia.

Why this dose and rate fit best: a 2 g dose hits the therapeutic level needed for bronchodilation without pushing the risk of adverse effects that come with higher doses or faster administration. A smaller dose may be subtherapeutic, while a larger dose or a much faster infusion increases adverse effects and is not the standard approach in this bundle.