Traveling with frozen medicine

I suppose that would work for the flight if you kept it in an insulated container, but that wouldn't last the entire trip, and obtaining dry ice on the go would be...well, really difficult. If it is sufficiently frozen initially, a constant supply of regular ice should keep it frozen thereafter, but even frozen H2O isn't always easy to find in Europe.

I don't have any other ideas, but have you checked with your eye doctor? You should also check with your airline about whatever plan you have, to make sure there's no problem bringing it on the plane in the passenger compartment (you don't want to check such valuable medication). I agree the biggest problem will be keeping it frozen for days after landing.

How long do you have to keep it frozen?

Dry ice is allowed in your carryon by TSA, but it is limited to 2.5 kilos and MUST be in a container that allows venting cf the CO2. It is supposed to be labeled too.

http://www.faa.gov/about/office_org/headquarters_offices/ash/ash_programs/hazmat/media/materialscarriedbypassengersandcrew.pdf

Your airline may have different restrictions so check with them too.

I use eye drops that just need to be kept cool, not frozen. My eye doctor didn't give me any ideas, so I searched on-line and found a Frio insulin cooling wallet. I don't know if you could find something like that to keep your drops frozen until you could get more ice during your travels. Or maybe this wallet would help kept them frozen until you got more ice. Perhaps your pharmacist could help you out with ideas.

Generally ice will not keep something frozen especially if the freezing point is something lower than ice. Only real choice is dry ice. I would check ahead with your hotels to see if they know of a local source for dry ice. Dry ice has the same use and function in Europe as the US so it will be available. Just finding it is the problem.