Responses

I went to check, he didn't know at first but in the chapter 46 he knew ( i forgot how ) and confronted the guy that sold the drugs to him asking him if he knew the side effects, who was the one providing the goods ( which that guy didn't who it was ) and that he lied to him ( the guy lied to Jiheon about having no side effects )
I think Jiheon knows that the drugs have side effects right ? so I don't think he will let Wooju eat that anymore ( or maybe he will... )