Also be aware that some medications should be refrigerated, but NOT FROZEN. Doubtful that any on-board refrigeration will be able to maintain a tight temperature range, given the condition of some of the in-flight meals I've been served (frozen lettuce). This could also be a problem if you use dry ice (which is around -70 C with the vapor phase being well below the freezing point). Check with your pharmacist or search the package labeling for guidelines. And in a related note, some refrigerated medication is actually quite stable for ~28 days at room temp and only needs to be kept cold for long term storage. Yours might be one of these. But it might not.