Safe to Get Restylane and Botox While on Antibiotics?

No worries here - they can be done on the same day and while on antibiotics. The one thing you may need to consider, however, is whether you've been taking motrin, aspirin or other pain relievers that may increase your bruising after the procedure.
I always recommend that if you can, stop any aspirin or aspirin like drug about a week or so before the procedure. This decreases the likelihood of bruising significantly.

I agree with the other plastic surgeon that no cosmetic procedure, even an injectable procedure in the office, should be performed if the patient has an active infection and is on antibiotics. I would reschedule the procedure until the patient is healthy.
Most Botox cosmetic injections are in the upper face (the frown lines, the forehead, and the crows feet), while many soft tissue fillers such as Restylane, Juvederm, and Perlane are most commonly injected into the mid and lower face. Nasolabial folds or "smile lines" are the most common area to have injections, followed by the oral commissures (corners of the mouth) and lips.
There are times when Botox can be used in the lower face and soft tissue fillers such as Restylane may be injected in the upper face. The only potential problem that could be if the Botox and Restylane were injected in the same area of the face at the same time simply because you DON'T want to massage an area that Botox was injected and you DO want to massage an area that Restylane was injected to soften and smooth the injectable. The Botox can diffuse more from massaging which could potentially cause problems such as a droopy eyelid.
If for some reason you were planning on having any Restylane injected in the glabella (between the eyebrows) or tear trough (junction of lower lid with the cheek) then I would NOT recommend having Botox and Restylane at the same time and I would probably stage it 2 weeks apart with the Botox first.
Hope this helps!