Escaping the Archduke of the North’s Obsession

Isabella had given a love potion that she created to the male protagonist of this novel, Prince Kyar, the Northern Archduke.
Now, she was accidentally married to him!
“I’m doing this because of the strange medicine you made. So, you take responsibility.”
She tried to save him when he almost died but…. How did this happen?
After drinking love potion, Prince Kyar became obsessed with Isabella and even forced her to go to his castle with him.
There’s only one way to get out of this situation and that was—
To make an antidote for him, that’s all.