New here - topical to oral?

Hey everyone, Nice to “meet” everyone, but sorry that we are all here. I’ve been on topical rogaine (5%) for almost 3 months now. I’ve just started seeing about 5 or so baby hairs sprouting up, but my scalp is so irritated. It’s red, itchy, and there’s a little bumps starting to form everywhere. I’m thinking about switching to the oral medication (which I have a prescription for) because I think my skin will tolerate it better. I’m just wondering what would be the equivalent dosage of oral medication that matches the 5% once a day? I don’t want to go backwards and shed all over again.