Which two agents are listed as bronchodilators?

• A. Theophylline and Tiotropium bromide
• B. Albuterol and Salmeterol
• C. Ipratropium and Montelukast
• D. Fluticasone and Budesonide

Answer: (A)

Bronchodilators relieve airway constriction by relaxing the smooth muscle of the airways. Theophylline works by inhibiting phosphodiesterase enzymes, which raises intracellular cAMP in airway smooth muscle, leading to relaxation; it also blocks adenosine receptors that can promote constriction. Tiotropium bromide is an antimuscarinic drug that blocks acetylcholine on M3 receptors in the airways, reducing vagal-mediated bronchoconstriction and producing sustained airway dilation. Using these two together shows two distinct, effective mechanisms for bronchodilation: increasing cAMP to relax muscle and blocking parasympathetic constriction. The other options include anti-inflammatory drugs or leukotriene antagonists, which are not bronchodilators themselves, making Theophylline and Tiotropium bromide the correct pairing here.