This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: COPD and Asthma, Subject name: Medicine
Which one of the following is not recommended for the immediate treatment of acute severe asthma? 
Select and explain. 
A. Iptratropium, B. Magnesium sulfate, C. Hydrocoisone, D. Salmeterol
D: Salmeterol
Answer: D: Salmeterol 
Explanation: Due to slow onset of action , Salmeterol would not be useful .Ipratropium is an anti-cholinergic drug and is useful nebulization. Magnesium sulphate has been used in nebulization form ( surprisingly) or intravenous and antagonizes the effect of intra-cellular calcium. Hence it can reduce the bronchospasm Its used has been mentioned in current edition of Harrison. Hydrocoisone accentuates the effect of broncho-dilators and also inhibit production of leukotrienes.