I'd add to this professional advice that just because a package has a little card saying something is approved as a medication, this will not have any effect on security personnel.
They will only accept it as a medication and so exempt from the liquid container size rules if you can prove it was prescribed for you by an appropriate medical professional. If you really must take saline on board in quantities larger than KLouis recommends, just find a 3.4oz bottle instead. As this is the agreed world standard travel size, you shouldn't have any problem finding one.