My advice is to adhere to a near carb-free diet along with antifungal and antibiofilm protocol for 3 to 6 months in order to get yeast levels way down before doing anything with lactulose or probiotics for that matter. Nystatin enemas are also very helpful. Then you can start supplementing with probiotics (fermented veggies as well as high potency capsules) and prebiotics (lactulose and/or Galactomune). You should continue with antifungals but avoid harsh antifungals that can also kill probiotics: oregano oil, grapefruit seed extract, Colloidal Silver , high dose iodine, and turpentine. If you knock down the yeast sufficiently after months of antifungal therapy, when you take prebiotics such as lactulose the probiotics will flourish and bloom to a point of crowding out the remaining yeast. The pH of the colon will change favoring probiotics and disfavoring yeast. After 3 months on strict diet, antifungals and probiotics and prebiotics you should feel cured but it is right here you need to be careful. Don't immediately go onto a normal diet. Slowly re-introduce carbs. Go low and slow. I started by eating a serving of potatoes each day. Potato starch feeds the probiotics which coverts part of it into butyrate which heals leaky gut and feeds the intestinal mucosal cells. Rice crackers and chicken salad can be eaten as well. After several more months with limited carbs as well as probiotics and prebiotics you will eventually be able to eat normally but I would stay with a paleo diet and not eat any gluten or added sugar.

The amount of galactose in lactulose is tiny and should not cause problems if you sufficiently knock down your yeast levels before supplementing with lactulose.