This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Pharmacology
A 55-year-old female who is taking propanolol for the management of a cardiovascular disease experiences an acute asthmatic attack. Which of the following drugs would you prescribe to attenuate this asthmatic attack? 
Select and explain. 
A. Cromolyn sodium, B. Salbutamol, C. Beclomethasone, D. Ipratropium bromide
D: Ipratropium bromide
Answer: D: Ipratropium bromide 
Explanation: (Ref: KDT 6/e p222) Inhaled b2 agonists are the agens of choice for termination of acute attack of bronchial asthma. However, as the patient is receiving b-blockers, treatment with b2 agonists will be ineffective (receptors are already blocked). Therefore, other bronchodilators like anticholinergic agents (ipratropium) or methylxanthines (theophylline) will be useful in such a case.