Removing carbon filter when medicating

Almost every aquarium treatment and medicine clearly states that the
carbon filter should be removed before adding the medicine. However, I
have never come across any guidelines for how long it should be
removed for. It seems such an obvious question, but really I don't
know whether they mean an hour, a day, a week?

If I put it back too soon presumably I may make the treatment
ineffective, whereas if the carbon filter is normally doing some good
(which I think it is) then by leaving it out for too long, say a week
or two, I could be harming my fish?

How long do people normally remove the carbon for when treating?

Peter.