This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
A patient came to the casualty with acute attack of asthma after starting treatment of glaucoma. The causative drug is 
Select and explain. 
A. Timolol, B. Betaxolol, C. Clonidine, D. Acetazolamide
A: Timolol
Answer: A: Timolol 
Explanation: Ans. (a) Timolol(Ref: Kanski 7/e, p. 383; Katzung 12/e, p. 158)Timolol is a non-selective beta blocker and thus acts on Beta 2 receptors also, leading to broncospasm and exacerbation of asthmaBetaxolol is a cardioselective (beta 1 blocker) and thus is free from this side effect