Antibiotic causes weight loss?

Since the beginning of the week I have been struggling with a 500gm gain for no particular reason. Not binged, not eaten more than I usually do.

Yesterday I started on a course of augmentin as I had a infection in my gum after a visit to the dentist. Dont want to lose the tooth. Today the 500gms have gone plus an extra 100gms so on a new lower weight!

Something to do with inflammation? I cant live on antibiotics for the rest of my life! Got 4 more days tablets and maybe will then see a weight increase again. Can only be water and not fat.