I see. It's just in my mind, most of the way Joseph acts is psychological now. Even when Alexi phrases something as a request rather than an order, he still tends to do it whether he likes it or not. That's not the potion forcing him, as it doesn't trigger with simple requests as it does with order. That's his own learned loyalty and submissiveness. In some ways, he's actually worse off than a hard broken slave, because there isn't an antidote for that. Worst of all, right now, he doesn't want to be free. Or rather, he does, but he's so convinced that he doesn't deserve freedom that he would rather stay a slave. Alexi will be hard pressed to even get him to take the antidote. 

Anyway, all of that is a while off.