I get my medication shipped and it cannot get above a certain temperature (insulin). It arrives with in a cheap styrofoam cooler with a frozen pack and a cold pack. It seems to hold for a couple of days. I do the same in my travels. I have two frozen packs and an insulated lunch box. I have never had one melt in six hours. The insulin stays cold for 8-10. For insulin that I don't need to refrigerate but keep from getting over 80 degrees I use something called a Frio. It can keep insulin from getting too warm for a couple of days. I used it for travel to Bangkok and Hong Kong and Singapore and it worked really well. Again, that is for my insulin once I start using it and have too keep it at cool room temperature.
As others have said, I have gotten some ice in a bag when I thought my cold packs might be getting too warm, but they seem to work pretty well for a good long time.
I have accidentally frozen my insulin by putting it in a poorly controlled hotel room refrigerator. That was a $300 mistake I will not make again. I don't use hotel fridges for insulin anymore. I use the freezer part (if available) to refreeze the cold packs one at a time while I keep the insulin in the cooler with the other. I have these little tabs that change color if the inside gets too warm, but they have never gotten to that point.