YTA

He is at fault for ruining your pills, but unless it was intentional, he is not an asshole in that situation. Everyone makes mistakes.

It sounds like you were mad in the moment, and yelled at him. That actually doesn't make you the asshole. It's understandable, someone else did something dumb and made you mad. Similarly to him, you are not an asshole for acting rude, aggressive and irrationally, everyone makes mistakes.

What you are the asshole for, is not recognizing your rude and emotional actions in that moment. Demonstrated by your responses and this post.

If your friend made a honest mistake, and your response is to be rude to them, then it is understandable that your friend view your response as an intentional attack as apposed to his unintentional mistake and refuses to apologize until you show that your response was just as unintentional as his was. It is therefore your responsibility to show him that your behavior was unintentional. After which, he would be the asshole if he does not reciprocate the apology.

The only exception is if you also believe his mistake as intentional and malicious and yours as unintentional. In which case there would be no assholes.