Visitors to Egypt are advised to bring an adequate supply of their own medication. Only bring what you need for yourself to see you through until the end of your stay. Be warned, some local medications/drugs are not allowed in Egypt, so to be on the safe side, bring a letter from your GP or other proof that you need the medication. Do not bring medication for other people.
A stomach upset followed by diarrhea is the most common form of illness for travelers to Luxor. To avoid the problem, the usual recommendation is to eat only thoroughly cooked food and fruit you have peeled yourself. In practice, stomach problems are not necessarily caused by food, in fact one of the biggest potential hazards is money, which changes hands all the time.
There is also a degree of understanding that the change in climate can also affect your stomach, especially if, after a hot day trekking over the hillsides, you immediately sink something ice-cold. It is better to let yourself acclimatize a little first. You are advised to bring your own hand sanitizer or wipes. There are plenty of well stocked pharmacies in Luxor.
Only drink sealed, bottled water, and try and avoid ice cubes.