Who cares if this drug exists IRL, and/or if it works as shown in this scene ?Yep! And anyone who has taken it or anyone who works in the field has complained about it to Ocean.
Just my two cents here: I think the scene would have been much stronger if Sasha had gone up and done everything the same without the pill. Of course, the pill would not have created that kind of response in him. But having her there, holding his hand, and talking him through the attack would have been extremely powerful.
In my opinion, the purpose of this scene is to show that Sasha knows what's happening to the MC, and that she's carrying something to remedy it. What this means is that she suffers from this same problem to the point of carrying pills to treat it, or that someone very close to her has this kind of problem.
It also justifies the fact that, in the near future, the MC may carry these pills with him.