Answer:
I beleive this one would be a bit of a matter of opinion when it comes down to it, but personally I would call it a bit unethical.
Explanation:
Escpecially when it comes to something like medication, it feels unethical to be advertising yourself as the only brand that will work. In my mind unique selling proposition would be focusing on what differentiates your product from others (example, my product can provide 48 hour vs other brands that only offer 24 hour) Simply stating their brand is the only solution feels unethical and does not provide ample evidence of this claim to customers in my opinion. I don't think it would be considered illegal, but in my mind its tiptoeing the line of ethics.