Definition by Wonder Me!: 

Competitive antagonists have to compete with other agonists for receptors. And, once it already binds to the receptors, it still can be replaced by agonists if the agonists concentration is high enough to displace competitive antagonists.

Clinical example:

Naloxone(1)

Why it works?: 

Naloxone is an infusion because it has short half-life. Thus, at first, its concentration exceeds opioid concentration. But then, due to its short half-life, its concentration becomes less than that of opioid. This makes pt becomes unconscious again. Therefore, constant naloxone drip is needed. (2)  

 

 

MCQ resources:

https://books.google.com/books?id=7PXn6BVhtT0C&pg=PA9&dq=%22competitive+antagonist%22+naloxone&hl=en&sa=X&ved=0ahUKEwjJqOTP2_HLAhUKlYMKHTFACO0Q6AEIJTAA#v=onepage&q=%22competitive%20antagonist%22%20naloxone&f=false

Citations:

(1) http://emedicine.medscape.com/article/815784-medication

(2) https://books.google.com/books?id=jDWXAwAAQBAJ&pg=PA707&dq=%22competitive+antagonist%22+naloxone&hl=en&sa=X&ved=0ahUKEwjJqOTP2_HLAhUKlYMKHTFACO0Q6AEIMDAC#v=onepage&q=%22competitive%20antagonist%22%20naloxone&f=false