This applies particularly to oral medication. You may be able to purchase anti-histamines at your destination but you may find you can’t purchase the non-drowsy kind.
Plasters and bandages are the most important thing if you are camping or planning a remote vacation. You never know when someone will get hurt out in nature.
Pack an over-the-counter remedy that contains “loperamide” such as Imodium as well as sachets of an oral rehydration remedy like this one will replace lost fluids and restore salt levels.