Probiotic spacing question

[springmum]

My DS (21 months) is taking one dose of abx at 7:30 am. (as prescribed)

I've been waiting 2-3 hours to give him his probiotics (kirkman multi-flora)
Then giving him another dose of probiotics (kirkman bifido) in the afternoon/dinner time.

Is there any reason I should adjust when I give the probiotics? (Farther apart from the abx I guess is what I'm asking, which might be a silly question but I'm really tired today )

[sbgrace]

I do three hours but I've seen others say they do half way between. I think the ideal spacing would be at three hours and then again at half way.

[springmum]

Thank you