My son took the neomycin with meals but no diary products.
The lactulose doesn't matter if you take it with meals or not, but only one dose will do the trick. Actually, take it in the afternoon or evening of the day before your day off when you won't need to go to work or school, and can stay home with diarrhea. Once the diarrhea stops, you can go out that evening. Then start the metronidazole (which is a recommended Antibiotic too) right after the diarrheas or the following morning. Make sure you don't miss a dose. AFter you finish with the metronidazole, start your probiotics, with a higher dose at first, and then tapering down to the normally recommended dose, ask your pharmacist (or the person who sells it to you) what is the normally recommended dose for the specific one they give you.