It depends on the reason for their agitation. If they’re having a paranoid moment then you need ti tell them the truth to help them out of it.

If you lie they might pick up on it and that kills the trust they have in you.

You don’t have to press them to take meds they don’t want to take, but if you lie about why you’re stopping (“maybe you’re right”), instead of telling the truth about why you’re stopping (“I don’t want to break our therapeutic connection by pushing you”), it can make things backslide.