Overdoses have their peak effect generally within an hour of administration. While I cannot say if a particular dose is harmful in a particular person, I can say that by the time I am answering this, the worst complciations would very likely have already happened. Zenflox is generally not given to non-adults anymore because of entirely theoretical effects on the development of bones and cartilage. There are extremely few actual cases where any damage has been seen. They are dependent on LONG TERM DOSING (weeks, not days). so, theoretically there could be damage to tendons, cartilage, or even kidney, in practice, no. Furthermore, as an antibiotic it was developed to hit something the germs have and we do not. They are relatively safe compared to aspirin, tylenol, water, sunlight.... And tripling the exposure to antibiotics is unlikely to do anything while tripling any of the others mentioned would be quite concerning. On the other hand, green stools are very unlikely to mean anything at all and are generally never treated. The amount of vegetables or food dyes is the general cause and not the gut.