Can too much medicine harm hamsters?

hi, four weeks ago my two robo hamsters got mites. we took them to the vets and they gave us some medicine that you dab on their skin/fur. we got told to use it two weeks after then, and four weeks after then (today) and i held them while my mum put it on them, and we left them alone. this was about an hour ago and now their fur is still quite wet and they are rubbing against things trying to get it off them. we don't think we have but if we've put too much medicine on them, would it be bad for them/hurt them?