We used Gerber Soothe for our little one. When I was EBF, I gave her drops but now that I supplement with formula, I just use the Soothe one and stopped the drops.
We used bio gaia drops for my son when he was on antibiotics. The ped said there's no real evidence that they help, but that they wouldn't hurt either, so we went ahead and used them. They were pricey, around $20 a bottle if I'm remembering correctly?
(edited to add) - I believe the reason why our ped wasn't strongly recommending them was that in order for probiotics to really compensate for loss of "good bacteria" in the gut during a course of antibiotics, you'd have to take them some time in advance of starting the antibiotics. So taking them at the same time or after the fact would probably have no effect.
Re: Probiotics?
(edited to add) - I believe the reason why our ped wasn't strongly recommending them was that in order for probiotics to really compensate for loss of "good bacteria" in the gut during a course of antibiotics, you'd have to take them some time in advance of starting the antibiotics. So taking them at the same time or after the fact would probably have no effect.