Which drug is an anti-asthmatic bronchodilator?

• A. Salbutamol
• B. Budesonide
• C. Montelukast
• D. Theophylline

Answer: (A)

The question tests knowledge of which medication acts as a bronchodilator specifically used in asthma. Salbutamol is a selective beta-2 adrenergic receptor agonist. When it binds to β2 receptors on bronchial smooth muscle, it activates adenylate cyclase, increases cAMP, and causes the smooth muscle to relax, producing rapid bronchodilation. This makes it the classic fast-acting rescue bronchodilator in asthma.

The other options are not bronchodilators in the same immediate sense. Budesonide is an inhaled corticosteroid that reduces airway inflammation over time but does not quickly open the airways. Montelukast blocks leukotriene receptors to reduce inflammation and bronchoconstriction rather than providing immediate bronchodilation. Theophylline is a methylxanthine that can bronchodilate by inhibiting phosphodiesterase and increasing cAMP, but its use is limited by a narrow therapeutic window and interactions, so it’s less representative as a typical anti-asthmatic bronchodilator.