Your guide will have a first aid kit all the time while you are on the trek, which includes some pain killers, bandages, small bandages to prevent blisters, an oxygen tank, pills for the case of diarrheas, and similar.  At any time of the trek please feel free to ask for anything you may need, however, if you need any special medication or you have a special medical condition, please, contact your doctor to get the best advice before the trek.