As a smart travelers you should pack all the essential medications even though you don't need it. You'll never know, you might need it on your next trip to Europe, or any other places you plan to visit. Let me give you some input on what to bring or pack for your first aid.
1. Imodium
This one needs to be on your no. 1 list. You know how uncomfortable it is when your stomach make some problem in the middle of your bus trip. This will not cure your problem but at least it will make it stop temporarily .
2. Rehydration Salt
When your having diarrhea during your travel, of you need to rehydrate yourself to prevent from dehydration. They come in convenient pack/sachet that need to be dissolved in clean water and drunk.
3. Eye droppers
This is essentials to those travelers that are using contact lenses or to those that have dry eyes. This is also useful to travelers heading to somewhere dusty areas. It will give eye relief from irritation and wash off irritants and backteria.
4. Anti-Nausea Medications
You know how nasty a bus ride can be. This need to be in your first aid kit to save the person sitting next to you from showering your vomit. :)
5.Allergy Medication
This is also in case if you happen to eat something that can trigger your allergy. Always bring this medication if you don't want to end up in a hospital. You know how difficult it is when allergy strike you on you trip.